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UNIVERSITY 
OF    ILLINOIS 

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UNIVERSITY  OF  ILLINOIS, 

Agricultural  Experiment  Station. 


URBANA,   MARCH,    1897. 


BULLETIN  No.  47. 


*BROOM-CORN  SMUT. 

RELATIONSHIP. 

Related  plants.  Broom-corn  is  placed  by  botanists  in  the 
genus  Andropogon  (Sorghum),  one  of  the  prominent  genera  of 
the  grass  family.  Closely  related  to  this  plant  are  a  number  of 
other  cultivated  forms  commonly  known  as  sorghum,  durra,  Kafir 
corn,  Jerusalem  corn,  etc.  These  are  considered  by  Hackel  as 
descended  from  a  common  ancestor  and  are  therefore  placed  by 
him  as  varieties  under  the  species  Andropogon  Sorghum,  of  which 
broom-corn  is  designated  as  Andropogon  Sorghum  var.  technicus. 
In  different  parts  of  the  world,  usually  in  the  warmer  regions,  cer- 
tain of  these  varieties  have  assumed  considerable  importance ; 
especially  during  the  last  few  years  all  of  them  have  been  more 
largely  cultivated  in  the  United  States  and  seem  to  merit  this 
increased  attention.  Any  fungus  or  insect  found  at  work  on 
them,  therefore,  may  be  considered  of  direct  economic  importance, 
especially  when  serious  injury  is  inflicted. 

Related  smuts.  It  is  the  purpose  of  this  article  to  discuss  at 
length  one  of  the  fungous  troubles  of  this  group  of  plants — a  fungus 
that  is  commonly  designated  as  smut.  As  there  are  several  species 
that  have  been  found  on  one  or  another  of  these  plants,  it  may  be 
well  to  consider  briefly  all  of  the  smuts  before  proceeding  to  the 

*For  those  who  may  wish  merely  to  get  from  this  bulletin  the  practical  method  ot 
preventing  broom-corn  smut,  there  has  been  prepared  at  the  end,  under  "  Prevention  of 
broom-corn  smut,"  directions  for  the  use  of  hot  water  in  the  treatment  of  broom-corn 
seed.  Also  under  "  Summary,"  immediately  preceding  the  above,  are  given  briefly  some 
of  the  chief  points  that  the  bulletin  presents.  The  writer  wishes  to  acknowledge  indebt- 
edness and  return  thanks  to  the  several  botanists  and  to  the  growers  and  dealers  in 
broom-corn  who  have  conferred  such  favors  as  the  loan  of  specimens,  references  to  liter- 
ature, information  concerning  the  injury  and  loss  caused  by  the  smut,  etc.  373 


374  BULLETIN  NO.  47.  {March, 

discussion  of  this  particular  one.  From  Cairo,  Egypt,  there  has 
been  reported  a  smut  in  the  flower  parts  of  a  variety  of  Andropogon 
grown  there.  In  this  the  spores  adhere  in  small  round  balls,  and 
so  the  fungus  is  placed  in  the  genus  Sorosporium  (Sorosporinm 
Ehrcnbergii},  although  originally  the  specimen  was  incorrectly 
referred  to  a  species  of  Ustilago  (Ustilago  Reiliana*}.  So  far  it 
seems  to  have  been  collected  from  that  locality  only.  On  the 
same  plant  from  central  Asia  another  smut  has  been  reported, 
which  by  its  discoverer,  Sorokine,  was  described  as  a  type  of  a 
new  genus,  Endothlaspis ;  but  later  it  has  been  placed  by  De-Toni 
doubtfully  in  the  genus  Cintractia  (Cintractia  Sorghi}.  Tracy  and 
Earle  report  a  single  specimen  of  this  from  Mississippi,  collected 
in  1888.  An  examination  of  this  specimen,  however,  shows  that  its 
spores  are  larger  than  those  of  Cintractia  Sorghi,  as  described  by 
De-Toni,  and  it  corresponds  so  closely  with  Ustilago  Reiliana  that 
it  seems  proper  to  consider  it  as  belonging  to  that  species.  There 
are  three  smuts  apparently  of  the  Ustilago  type  that  have  been 
found  on  one  or  another  of  these  varieties.  The  most  conspicuous 
is  head  smut  (Ustilago  Reiliana'),  which  turns  the  whole  panicle 
into  a  smutty  mass.  This  is  more  common  than  the  above,  being 
reported  from  Africa,  Europe,  and  from  two  or  three  places  in  the 
United  States.  The  second  one  (  Ustilago  cruenta)  occurs  in  less 
conspicuous  outbreaks  on  the  rays  of  the  panicle,  occasionally  on 
the  stem  itself,  and  in  the  flower  parts.  While  a  common  form  in 
certain  parts  of  Europe,  this  smut  has  not  yet  been  reported  in  this 
country.  The  third  form  ( Ustilago  Sorghi)  is  quite  similar  to  the 
second  but  limits  its  attacks  to  the  young  inner  flower  parts,  pro- 
ducing a  seed-like  body  filled  with  its  spores. 

Identity  of  broom-corn  smut.  A  comparison  of  the  specimens 
of  smuts  collected  on  the  sorghum-like  plants  in  Kansas,  Illinois, 
New  Jersey,  and  Wisconsin  with  European  specimens  of  the  above 
Ustilagos  leads  to  the  conclusion  that  the  smuts  so  far  collected  in 
this  country,  when  limited  to  the  reproductive  parts  of  the  flower, 
belong  to  the  species  Ustilago  Sorghi.  In  fact  this  is  the  species 
to  which  they  have  always  been  referred.  Ustilago  cruenta  and 
Ustilago  Sorghi,  however,  are  very  closely  related.  The  chief  dif- 
ferences between  them  that  can  be  gathered  from  an  examination 
of  descriptions  and  specimens  are  that  the  former  may  occur  on 
any  part  of  the  panicle  or  even  on  the  stem,  while  the  latter  is 
confined  to  the  flower;  that  the  former  has  spores  that  average 
larger  and  are  more  variable  in  size  and  shape  than  the  latter;  that 
the  individual  spores  of  the  former  are  more  apt  to  have  a  reddish 
tint  while  the  latter  usually  have  a  distinct  olive  tint. 

*  See  de  Thiimen  Mycotheca  universalis,  No.  725. 


1897.}  BROOM-CORN   SMUT.  375 

The  reason  for  doubting  the  identity  of  our  specimens  was 
caused  by  the  description  of  the  life  history1  of  Ustilago  cruenta  as 
given  by  Brefeld,  especially  the  germination,2  which  seems  to 
agree  very  closely  with  what  we  have  learned  concerning  the  smut 
on  broom-corn,  and  also  by  the  statement  made  by  him  that 
Ustilago  Sorglifi  did  not  germinate  in  water,  which  seems  to  be  a 
very  characteristic  thing  with  the  smut  with  which  we  have  dealt. 
It  is  barely  possible  that  the  Ustilago  with  which  his  chief  investi- 
gations were  carried  on  might  be  considered  by  some  botanists  as 
Ustilago  Sorghi,  instead  of  Ustilago  cruenta,  as  they  were  with  a 
smut  that  was  entirely  confined  to  the  inflorescence.  But  certainly 
the  evidence  as  a  whole  justifies  the  conclusion  that  our  American 
specimens  belong  to  the  species  called  Ustilago  Sorghi. 

This  point  in  its  identity  having  been  settled,  another  diffi- 
culty arose  when  a  study  was  made  of  the  spore  formation  of  the 
fungus.  This  showed  that  it  agreed  in  this  respect  with  the  genus 
Cintractia  rather  than  with  Ustilago,  and  if  we  are  to  regard  these 
as  distinct  genera,  our  fungus  must  be  considered  as  belonging  to 
the  former.  Endothlaspis  Sorghi  of  Sorokine,  as  has  been  stated, 
is  now  referred  by  De-Toni  questioningly  to  Cintractia,  and  what 
was  described  originally  as  a  quite  distinct  smut  is  really  rather 
closely  related  to  our  form.  It  is  not  unlikely  that  an  examina- 
tion of  the  spore  formation  of  Ustilago  cruenta  would  also  show 
something  of  this  character.  A  careful  examination  of  the  type 
specimens  and  of  collections  obtained  from  the  different  countries 
where  these  smuts  have  been  reported,  together  with  a  study  of 
their  spore  formation  and  germination,  is  needed  to  bring  out  their 
true  systematic  relationships.  However,  having  settled  upon  the 
identity  of  our  form  as  a  Cintractia  and  as  the  species  commonly 
called  Ustilago  Sorghi,  let  us  next  consider  its  hosts  and  distribu- 
tion. 

HOSTS   AND   DISTRIBUTION. 

/;/  general.  This  smut  has  been  reported  from  a  number  of 
the  countries  of  southern  Europe,  also  from  Africa,  Asia,  and  the 
United  States;  and  has  for  its  host  several  of  the  different  varieties 
of  Andropogon  Sorghum.  It  was  brought  to  the  United  States 
through  imported  seed  of  these  plants.  Just  when  and  where  it 
first  made  its  appearance  it  is  impossible  to  state ;  but  from  the 
ease  with  which  it  attacks  broom-corn  it  was  probably  at  the  place 
where  that  plant  was  first  largely  grown.  The  first  printed  refer- 
ence that  has  been  found  is  that  made  by  Trelease,  in  his  "  Pre- 
liminary List  of  Parasitic  Fungi  of  Wisconsin,"  printed  in  1884. 

1  Untersuchungen  aus  dem  Gesammtgebiete  der  Mykologie  u:  43-51.  9  Ibid 
5:  91-93.  8Ibid  12:  120 


376  BULLETIN  NO.  47.  [March, 

In  this  he  mentions  the  finding  of  the  fungus  at  Madison,  and  also 
states  that  Sturtevant  reports  it  from  New  York  and  Farlow  from 
the  District  of  Columbia,  in  all  three  cases  on  plants  raised  from 
imported  Chinese  seed.  Professor  Farlow  in  answer  to  inquiries 
concerning  the  Columbia  specimen  writes  that  it  was  sent  to  him 
from  the  Department  of  Agriculture  at  Washington  and  was 
taken  from  sorghum  grown  in  New  Jersey  in  1882.  In  1889 
Webber  reported  the  finding  of  the  smut  on  Millo  maize  in 
Nebraska,  and  in  1890  Failyer  and  Willard  found  the  same  on 
several  imported  varieties  grown  for  the  first  time  at  the  Kansas 
Experiment  Station.  Professor  Hitchcock  in  answer  to  a  letter 
gives  the  following  plants  upon  which  it  has  been  collected  in 
Kansas:  sorghum  (Early  .Amber,  Rangoon,  Red  Liberian,  and 
many  unknown  varieties),  broom-corn,  Kafir  corn.  Though  not 
reported  from  Ohio  so  far  as  can  be  learned,  it  probably  has 
occurred  there,  as  considerable  broom-corn  has  been  raised  in 
that  state. 

In  Illinois.  The  first  collections  made  in  Illinois  that  are 
represented  in  the  herbarium  at  the  University  of  Illinois  were 
those  made  by  M.  B.  Waite  in  August,  1887,  at  Urbana.  In  1888 
in  the  Proceedings  of  the  American  Society  of  Microscopists, 
Burrill  notes  the  smut  as  occurring  in  this  state  on  both  broom- 
corn  and  sorghum,  and  this  is  the  first  printed  reference  to  the 
smut  here  that  has  been  found.  No  further  collections  or  study 
was  made  until  the  spring  of  1894,  when  John  Marten,  assistant  to 
the  State  Entomologist,  in  studying  the  insect  pests  of  broom- 
corn  at  Arcola,  brought  specimens  to  the  botanical  department 
with  the  report  that  this  was  considered  one  of  the  worst  pests  of 
the  plant  in  that  vicinity.  The  study  of  the  fungus  in  its  relation 
to  broom-corn  was  then  undertaken  by  the  botanical  department 
of  the  Experiment  Station,  the  results  of  which  are  given  in  this 
bulletin. 

INJURY   AND   LOSS. 

Effect  of  attack.  The  importance  of  a  fungous  disease  depends 
in  great  part  on  the  place  and  character  of  its  attack.  What  is 
the  effect  of  this  fungus  upon  its  host?  As  with  the  smuts  of 
wheat  and  oats,  one  cannot  tell  the  infected  plant  from  the  free 
until  the  floral  parts  are  protruded  through  the  upper  leaves. 
Examination  then  shows  that  the  infected  plants  have  the  place 
of  the  seed  occupied  by  a  usually  enlarged  body,  having  on  the 
outside  a  reddish  covering  and  within  a  dusty  mass  of  spores. 
All  the  seeds  of  an  infected  panicle  are  usually  destroyed.  The 
first  noticeable  injury,  then,  is  the  prevention  of  seed  formation. 


BROOM-CORN   SMUT.  377 

In  the  case  of  broom-cornr  this  loss  is  not  nearly  so  serious  as  in 
the  case  of  those  cereals  that  are  raised  especially  for  the  seed. 

An  examination  of  the  brush  of  an  infected  plant,  unfortu- 
nately, shows  that  it  is  of  a  very  inferior  grade,  usually  almost 
worthless.  Here,  then,  is  a  much  more  important  loss,  for  the 
brush  is  the  part  for  which  broom-corn  is  raised.  Good  broom- 
corn  has  the  rays  of  about  uniform  thickness  and  length  and  all 
springing  from  a  series  of  very  contracted  nodes  so  as  to  give 
them  about  the  same  point  of  origin.  In  the  case  of  infected 
plants  these  internodes  are  usually  elongated,  and  the  rays  are  of 
unequal  lengths,  so  that  there  are  a  series  of  irregular  rays  arranged 
on  an  elongated  and  thickened  central  axis — qualities  very  unde- 
sirable. Among  growers  of  broom-corn  this  elongated  and 
thickened  axis  is  not  always  recognized  as  the  work  of  the  fungus. 
This  is  probably  due  to  the  fact  that  occasionally  plants  apparently 
free  from  the  fungus  show  brush  of  this  character.  Such  are  but 
tendencies  to  a  reversion  toward  the  original  type  of  the  plant; 
and,  possibly,  even  in  such  cases  an  imprisoned  vegetative  state 
of  the  fungus  cut  off  from  spore  formation  may  at  times  be  the 
inciting  cause.  It  is  a  fact,  however,  that  in  the  many  hundreds 
of  smutty  panicles  examined  this  tendency  to  spread  out  the  con- 
tracted axis  was  always  more  or  less  manifested.  The  number  of 
large  normal  sized  rays  is  also  less  on  such  a  plant.  For  instance, 
in  each  of  two  different  varieties  the  principal  rays  were  counted 
on  ten  free  and  ten  affected  plants  selected  at  random.  In  every 
case  the  number  in  the  free  plants  exceeded  those  in  the  infected, 
while  the  average  for  one  was  fifty-five  on  free  plants  and  thirty- 
three  on  infected,  and  for  the  other  was  forty-eight  on  free  and 
thirty-seven  on  infected  plants.  The  energy  in  such  plants  has 
gone  into  the  elongated  axis  and  not  in  enlarging  all  the  rays. 

Smut  may  also  produce  some  damage  by  the  spores  settling 
on  the  brush  when  this  is  gathered  with  moisture  on  it.  These 
stick  to  the  plant  when  the  moisture  evaporates,  and  although 
they  may  in  part  be  shaken  off  the  appearance  of  the  brush  is 
still  \  ery  apt  to  be  affected.  This,  however,  must  not  be  con- 
fused, as  it  is  by  some,  with  the  trouble  that  arises  when  broom- 
corn  is  stored  wet  or  in  a  damp  place.  Under  such  a  condition  a 
saprophytic  fungus  of  an  entirely  different  nature  is  very  apt  to 
appear  on  the  plants,  causing  them  to  have  a  deadened  color  and 
to  become  blackish  where  the  fungous  threads  show.  This  trouble 
affects  very  decidedly  the  color  and  strength  and  consequently 
the  value  of  the  brush.  Smut  is,  finally,  a  bad  thing  because  of 
the  disagreeable  dust  that  is  produced  when  plants  so  affected  are 
thrashed. 


378  BULLETIN  NO.  47.  {March, 

Abundance.  A  second  factor  that  determines  the  importance  of 
a  fungous  disease  is  its  abundance  or  distribution.  What  per  cent, 
of  broom-corn  plants  are  infected  by  smut,  and  how  does  this  per 
cent,  vary  from  year  to  year?  In  1895  Mr.  Duncan,  of  the  firm 
of  Duncan  &  Tarbox,  broom-corn  dealers  at  Arcola,  said  in  re- 
sponse to  inquiries  that  broom-corn  had  been  raised  in  that  region 
for  thirty-five  years,  and  while  at  first  smut  was  not  noticed  it  had 
gradually  increased  in  amount.  Mr.  B.  F.  Cox,  a  dealer  at  the 
same  place,  also  expressed  a  belief  that  smut  was  more  abundant 
than  formerly,  and  gave  as  a  rough  estimate  that  -an  average  of 
one  per  cent,  of  the  plants  were  smutty.  An  examina- 
tion of  a  few  fields  in  the  vicinity  that  year  showed  them  usually 
with  less  than  one  per  cent,  smutted.  One  very  smutty  field, 
however,  gave  in  parts  of  it  twenty  per  cent.  The  few  growers 
seen  seemed  to  think  that  smut  was  less  than  usual,  though  a  year 
or  two  previous  it  had  been  unusually  abundant.  In  1896  letters  of 
inquiry  to  various  buyers  and  raisers  in  the  vicinity  of  Arcola  and 
Tuscola  brought  the  uniform  reply  that  it  had  been  a  year  in 
which  broom-corn  was  quite  free  from  smut. 

In  our  experiments  here  broom-corn,  raised  from  seed  such 
as  is  ordinarily  planted,  gave  in  different  plats  during  the  two 
years  yields  varying  from  one  to  twenty  per  cent,  smutty;  while 
that  raised  from  very  smutty  seed  gave  from  ten  to  fifty  per  cent. 
In  1896  the  plants  here,  unlike  those  in  the  broom-corn  district, 
were  unusually  smutty.  It  is  generally  true  that  the  seed  that  is 
ordinarily  planted  produces  plants  in  which  the  amount  of  smut 
varies  from  practically  nothing  up  to  three  to  five  per  cent.,  or, 
under  exceptionally  favorable  conditions  for  the  fungus,  a  still 
higher  per  cent,  may  be  expected;  while  seed  that  is  very  smutty 
is  always  likely  to  give  a  crop  with  considerable  smut,  the  per 
cent,  of  which  under  conditions  favorable  to  it  becomes  very  large. 

Value  of  crop.  The  importance  of  a  fungous  disease  depends 
lastly  upon  the  value  of  the  host  as  a  commercial  plant.  In  the 
United  States  broom-corn  is  largely  raised  in  parts  of  Kansas, 
Illinois,  and  possibly  in  a  few  other  states.  The  area  devoted  to 
its  culture  in  1895  was  estimated  at  over  two  hundred  thousand 
acres.1  Of  this  area  Kansas2  claimed  about  one  hundred  thirty- 
five  thousand  acres,  producing  a  crop  valued  at  over  one  million 
two  hundred  twenty  thousand  dollars.  The  next  year,  however, 
the  acreage  dropped  to  less  than  forty  thousand.  The  secre- 
tary3 of  the  State  Board  of  Agriculture  for  Illinois  gave  the  area  in 
this  state  for  1895  as  over  twenty-five  thousand  acres,  a  slight 

'Irrig.  Age  9:—  Ja.  1896.  2  Rep.  St.  Bd.  Agr.  Kans.  16:794.  1896.  3Statist. 
Rep.  111.  St.  Bd.  Agr.  Dec.  1895 :  5.  1895. 


BROOM-CORN   SMUT.  379 

decrease  from  the  preceding  year.  This  Illinois  acreage  gave  a 
yield  of  over  eighty-five  hundred  tons,  the  value  of  which,  esti- 
mated at  the  average  price  of  the  time,  was  over  three  hundred 
thirty  thousand  dollars.  Broom-corn,  while  raised  in  a  small  way 
in  a  number  of  different  counties,  is  extensively  grown  in  Coles 
and  Douglas  only,  situated  in  central  eastern  Illinois.  Here  it  is 
one  of  the  principal  crops,  amounting  to  three-fourths  of  all  that 
is  raised  in  the  state. 

Financial  loss.  Judging  from  the  above  facts  can  this  smut 
be  counted  as  an  important  pest?  In  other  words,  is  it  injurious 
enough  to  merit  attempts  at  prevention?  If  the  seed  of  broom- 
corn  was  the  part  for  which  the  plant  is  raised  (its  loss  when  at- 
tacked by  the  smut  usually  being  total  and  the  per  cent,  of  in- 
fested plants  being  easily  estimated)  the  loss  in  dollars  in  partic- 
ular cases  or  even  in  general  for  a  district  could  be  fairly  esti- 
mated, as  is  done  in  the  case  of  smutted  oats  and  wheat ;  but  as 
the  case  is  an  estimate  of  loss  would  be  largely  guess  work.  No 
aim,  therefore,  is  made  here  to  estimate  the  loss  other  than  to 
state  that  it  is  often  great  enough  to  make  preventive  measures 
desirable.  That  it  is  at  least  serious  enough  for  this  seems  to  be 
the  uniform  opinion  of  those  interested  in  the  culture  of  the 
plant.  In  order  to  determine  the  estimate  placed  upon  the  fun- 
gus a  number  of  letters  were  sent  to  prominent  growers  of  broom- 
corn  at  Arcola  and  Tuscola,  and  several  of  the  answers  to  three 
of  the  questions  asked  are  given  here  : 

1.  Is  smut  one  of  the  prominent  enemies  of  broom-corn,  and  would  it  be 
of  much  benefit  if  it  could  be  prevented? 

2.  Do  you  use  means  to  keep  broom-corn  free  from  it?     What? 

3.  How  does  it  injure  broom-corn? 

i.  Yes.  2.  Plant  seed  that  is  not  affected  with  it.  3.  By  blackening 
it  after  it  gets  wet  before  it  is  thrashed.  Most  of  the  heads  that  have  smut  on 
them  are  of  no  account. 

Arcola,  111.  W.  C.  CUPPY. 

i.  Smut  is  an  enemy  of  broom-corn,  and  it  would  be  a  decided  benefit  to 
prevent  it.  2.  The  means  we  use  is  to  select  seed  that  has  no  smut  on  it.  3. 
You  lose  the  head  that  has  smut  on  it,  and  if  the  cane  is  damp  when  you  seed 
it,  it  colors  the  rest  and  injures  the  sale. 

Tuscola,  111.  A.  B.  SAWYER. 

i.  Smut  is  one  of  the  enemies,  and  it  would  be  an  advantage  if  prevented. 
2.  I  am  careful  to  use  seed  that  has  not  been  infected  with  it.  3.  If  cleaned 
when  damp  or  with  dew  on  it  darkens  the  brush. 

Arcola,  111.  D.  S.  HARRIS. 

i.  Yes.  2.  No.  3.  It  makes  it  a  light  or  white  color  and  the  brush 
is  brittle  and  of  light  weight.  I  think  the  time  it  is  planted  and  the  season 
has  a  good  deal  to  do  with  it,  as  some  years  it  is  worse  than  others.  It  was 
the  worst  in  1893,  a  very  dry  season  after  the  tenth  of  June. 

Tuscola,  111.  NATHANIEL  MOORE. 


380  BULLETIN  NO.  47.  r_March, 

I.  Yes.  2.  Yes,  by  washing  in  copperas.  3.  It  makes  it  bad  to 
handle  all  the  way  through,  and  if  it  rains  while  it  is  on  the  table  in  the  field  it 
causes  it  to  turn  black.  I  think  that  it  is  in  the  seed  that  is  planted,  and  the 
longer  seed  is  planted  (that  is  seed  that  has  smut  in  it  or  in  the  field  from 
which  it  came)  the  more  smut  there  will  be. 

Arcola,  111.  CHARLES  WESCH. 

I.  Yes.  In  my  opinion  it  would.  2.  Only  by  trying  to  secure  seed 
free  from  smut.  3.  By  blasting,  causing  large  fiber  of  a  coarse,  worthless 
quality.  Also  when  cleaned  when  damp  it  adheres  to  the  other  heads,  turning 
them  black. 

Arcola,  111.  F.  G.  HASTEN. 

Let  us  now  turn  from  the  economical  consideration  of  smut 
and  study  it  in  detail  as  a  plant  in  its  various  phases  of  develop- 
ment. 

LIFE    HISTORY. 

Nature  of  smut.  We  have  been  proceeding  so  far  on  the 
assumption  that  the  nature  of  smut  is  understood  by  the  reader. 
It  is  a  fact,  however,  that  all  growers  of  broom-corn  do  not  realize 
that  smut  is  a  plant,  though  of  low  development,  just  as  much  as 
'is  broom-corn,  which  is  one  of  high  development.  The  vague  ideas 
held  by  some  may  be  illustrated  by  the  fact  that  such  think  smut 
is  the  result  of  insect  work,  or  that  it  is  a  "  bastard  growth  due  to 
the  effect  of  sorghum  on  broom-corn,"  etc. 

Smut  belongs  to  the  very  low  group  of  plants  called  fungi — 
plants  of  very  simple  development,  usually  of  very  small  size, 
and  destitute  of  the  power  of  directly  forming  their  food  out  of 
mineral  matter,  moisture,  and  gases.  This  being  the  case,  fungi 
must  get  their  food  from  either  dead  or  living  organic  matter. 
In  the  case  of  smut  it  gets  its  food  from  the  living  broom-corn 
plant,  and  so  it  is  called  a  parasitic  fungus.  Like  broom-corn 
it  has  a  vegetative  part  concerned  with  obtaining  the  supply  of 
food  and  with  growth,  and  a  reproductive  part  concerned  chiefly 
with  the  production  of  future  individuals  like  itself.  The  vegeta- 
tive part  is  technically  known  as  mycelium,  and  is  composed  of 
thread-like  cells  concealed  entirely  within  the  tissues  of  the  broom- 
corn.  The  reproductive  bodies  are  known  as  spores,  and  the 
multitudes  of  these  minute  cells  are  what  constitute  the  visible 
portion  of  the  fungus  in  the  "  smutted  "  parts  of  the  host. 

Spores.  The  character  of  the  visible  outbreaks  seem  to  vary 
somewhat  in  the  different  varieties.  This  is  probably  due  to  the 
differences  in  the  surrounding  tissues  or  other  peculiar  character- 
istics of  each  host.  In  general,  however,  a  somewhat  elongated 
and  thickened  seed-like  body  is  formed.  In  broom-corn  this, 
compared  with  the  normal  seed,  is  usually  a  slightly  enlarged  ovate 


BROOM-CORN   SMUT.  381 

or  oblong  formation.  A  careful  examination  of  these  while  young 
shows  that  they  have  taken  the  place  of  the  young  pistil  and  sta- 
mens, rarely  merely  the  former  while  the  latter  have  come  to  a 
somewhat  normal  development.  Frequently  these  parts  are  infected 
so  early  that  they  have  become  blended  together  and  the  identity 
of  the  stamens  entirely  or  nearly  lost  (pi.  3,  fig.  6).  In  1895  speci- 
mens were  found  that  varied  considerably  from  this  normal  type. 
Here  the  outbreaks  were  more  elongated  (half  an  inch)  and  with 
somewhat  closely  appressed  branches.  Evidently  these  repre- 
sented an  infection  of  the  whole  flower,  or  possibly  of  more  than 
one  flower.  The  specimens  were  thought  at  first  to  be  a  distinct 
species,  but  the  appearance  and  germination  of  the  spores  and  all 
gradations  between  this  and  the  normal  form  showed  the  two  to 
be  the  same  (pi.  3,  fig.  7  and  8).  The  difference  in  appearance  was 
evidently  only  the  result  of  an  earlier  and  hence  more  widespread 
spore  formation.  In  all  of  these  outbreaks  there  is  on  the  outside 
a  somewhat  reddish  membrane,  while  the  space  within  is  taken  up 
with  a  dusty  mass  of  spores,  save  in  the  center  where  there  is  a 
distinct,  slender  and  hard  mass  of  tissue,  referred  to  by  Winter  as 
the  "columella." 

Examined  under  the  microscope  the  individual  spores  have  a 
brownish  color  with  a  distinct  olive  tint,  though  in  mass  to  the 
naked  eye  they  are  of  a  very  dark  reddish  brown  color.  They  are 
single  celled  bodies  of  a  sub-spherical  shape  and  from  5  to  8 
thousandths  of  a  millimeter  in  diameter,1  though  varying  occasion- 
ally from  the  above  in  both  shape  and  size.  The  protoplasmic 
contents  fill  the  spore  and  are  frequently  somewhat  granular  so 
as  to  give  the  spore  wall  the  appearance  of  being  minutely  papillate. 

Germination.  When  placed  in  water  these  spores  germinate 
readily.  No  other  of  the  many  smuts  whose  germination  in  water 
we  have  tried  has  germinated  so  readily  and  vigorously  as  this.  It 
germinates  equally  well  as  soon  as  formed  or  when  a  year  old. 
Specimens  kept  in  a  dry  room  germinated  whenever  placed  in 
water  at  various  intervals  during  more  than  three  years,  though 
less  abundantly  and  easily  the  last  year.  De  Bary  states  that  von 
Liebenberg  caused  the  spores  to  germinate  after  being  in  the 
herbarium  six  and  a  half  years. 

The  general  character  of  the  germination  depends  on  the 
fluid  in  which  the  spores  are  placed.  In  water,  while  there  was  a 
difference  in  degree  between  different  spores  in  the  same  culture, 
and,  while  at  different  times  perhaps  all  conditions  were  not  ex- 
actly the  same  and  so  varied  the  character  somewhat,  still  the  gen- 

JThis  size  may  be  better  appreciated  by  the  many  readers  when  it  is  stated  that 
there  are  millions  of  these  spores  in  each  of  the  seed-like  bodies. 


382  BULLETIN  NO.  47.  [March, 

eral  phenomena  were  as  follows  :  Within  six  to  ten  hours  after 
being  placed  in  the  water  many  of  the  spores  show  the  beginning 
of  germination  by  the  appearance  in  each  case  of  a  minute 
hyaline  papilla,  which  gradually  grows  out  into  a  thin -walled  tube 
having  a  rounded  and  slightly  pointed  apex,  but  showing  no  con- 
striction where  it  emerges  from  the  spore.  Some  spores  have 
shown  this  stage  of  germination  within  three  hours  after  being 
placed  in  the  water.  This  germ-tube,  or  pro-mycelium,  elongates 
until  it  is  three  to  five  times  as  long  as  the  diameter  of  the  spore, 
this  being  accomplished  within  less  than  twenty-four  hours  after 
germination  begins,  frequently  in  about  half  that  time.  Two  or 
three  cross-partitions  are  now  formed  at  right-angles  to  the  tube, 
dividing  it  into  three  or  four  about  equal  cells.  These  septa  are 
rather  faint  at  first,  and  while  the  tube  is  filled  with  protoplasmic 
contents  are  not  always  clearly  made  out.  A  slight  staining,  how- 
ever, serves  to  bring  them  out  much  clearer.  At  the  end  of  one 
or  more  of  these  cells  a  short  and  usually  narrow  outgrowth  ap- 
pears which  bends  over  and  fuses  with  the  adjoining  end  of  the 
next  cell.  Usually  this  outgrowth  is  so  closely  appressed  that  it 
appears  as  if  the  septum  had  not  been  formed  clear  across  the 
tube  on  that  side  (pi.  5,  fig.  3).  These  form  the  so-called  buckle  or 
knee  joints,  and  the  tube  frequently  has  more  or  less  of  a  bend 
where  they  occur.  In  a  number  of  cases  these  buckle  joints  were 
seen  to  be  formed  by  the  union  of  protuberances  extending  from 
each  side  of  the  septum.  Not  infrequently  these  slender  out- 
growths are  less  closely  appressed  to  the  tube  and  make  quite  a 
growth  before  joining  the  pro-mycelium  at  some  more  remote 
point  (pi.  5,  fig.  2).  From  these  buckle  joints,  or  the  end  of  the 
pro-mycelium,  frequently  a  thread,  usually  much  more  slender 
than  the  main  tube,  grows  out  to  a  varying  length,  forming  what 
I  have  called  infection-threads,  because  of  their  similarity  to  those 
produced  by  the  sporidia.  If  these  threads  attain  any  consider- 
able length,  they  show  an  irregular  curving  rather  than  a  growth 
in  a  straight  line  like  the  pro-mycelium.  Sometimes  the  pro- 
mycelium  also  gives  rise  to  a  lateral  branch  near  the  base  of  about 
the  same  diameter  as  itself.  Sporidia  are  generally  produced, 
though  not  always  very  abundantly.  Occasionally  one  can  be 
seen  forming  either  on  the  end  of  the  pro-mycelium  or  at  the 
apex  of  one  of  the  cells.  It  appears  as  a  small  outgrowth  hav- 
ing a  very  narrow  connection  with  the  tube,  enlarges  gradually 
and  is  very  easily  broken  from  its  connection,  so  that  sporidia  are 
usually  only  seen  free  in  the  water.  Usually  they  did  not  germ- 
inate, neither  did  they  seem  to  reproduce,  yeast-like,  after  being 
formed.  Frequently  a  large  part  of  the  pro-mycelium  is  early  cut 


BROOM-CORN   SMUT.  383 

off  from  the  spore  by  an  abstriction  near  the  base.  These  free 
bodies  are  somewhat  like  sporidia  in  appearance,  but  can  be  told 
by  their  larger  size  and  the  presence  of  one  or  two  septa.  They 
go  through  the  same  development  as  if  remaining  connected  with 
the  spore. 

The  preceding  germinations  were  produced  chiefly  in  dis- 
tilled water;  but  when  large  numbers  of  spores  are  placed  in  the 
fluid,  as  was  usually  the  case,  possibly  a  little  nutritive  material  is 
also  introduced.  Whether  the  spores  are  immersed  in  an  abund- 
ance of  water  or  are  merely  covered  with  a  film  so  as  to  admit  of 
contact  with  the  air  has  also  something  to  do  with  determining  the 
character  of  germination.  In  the  latter  case  the  pro-mycelium  is 
more  apt  to  run  out  into  a  slender  thread  which  is  many  times  the 
length  of  the  pro-mycelium  and  not  so  sharply  marked  off  from  it. 
The  protoplasm  is  confined  to  the  distal  end  of  this  thread,  the 
empty  part  becoming  regularly  septate.  In  some  few  cases  I  found 
that  in  time  these  threads  even  gave  rise  to  sporidia  and  secondary 
sporidia.  The  sporidia  and  secondary  sporidia  are  also  more  apt 
to  be  formed  on  and  to  adhere  to  the  pro-mycelium. 

In  nutrient  solutions  the  chief  differences  observed  from  the 
preceding  were  the  more  luxuriant,  though  not  necessarily  more 
abundant,  germination,  and  the  formation  of  more  sporidia.  In 
the  cases  where  a  weak  nutrient  fluid  of  tomato-broth  was  used  the 
chief  differences  were  the  somewhat  larger  pro-mycelia,  the  pres- 
ence in  the  fluid  of  more  free  sporidia,  infection  threads  of  greater 
diameter  and  usually  of  greater  length.  In  beef-broth  this  luxur- 
iant growth  of  the  pro-mycelium  was  still  greater;  the  sporidia 
were  formed  very  abundantly  and  were  not  easily  detached ;  and, 
while  connected  or  when  fallen  off,  formed  secondary  sporidia  by 
the  yeast-like  manner  of  sprouting;  the  sporidia  were  also  larger, 
especially  in  diameter,  as  were  also  the  branches  or  infection- 
threads  that  were  formed.  When  the  beef-broth  became  weakened 
sufficiently,  the  sporidia  ceased  their  sprouting  and  formed  the 
narrow  infection-threads  quite  similar  to  those  usually  produced 
in  water  from  the  pro-mycelium. 

Infection  of  host.  This  apparently  takes  place  through  the 
penetration  of  the  epidermis  by  the  infection-threads  of  the  pro- 
mycelium  as  well  as  by  those  of  the  sporidia.  Entrance  into  the 
plant  can  occur  only  when  the  cells  are  young,  and  successful 
infection  only  through  that  part  of  the  plant  where  the  threads 
can  reach  the  growing  tip  of  the  plant  before  the  tissues  through 
which  it  must  pass  are  very  old.  Thus  the  germinating  seed  in  its 
early  stages  is  the  only  place  where  broom-corn  is  liable  to  become 
successfully  infected.  As  a  germinating  plant  becomes  older  and 


384  BULLETIN   NO.   47. 

its  tissues  harder  of  penetration  by  the  threads,  infection  becomes 
less  possible  until,  at  the  time  when  the  plant  breaks  through  the 
ground  and  its  first  leaves  show,  it  is  practically  exempt  from  suc- 
cessful infection.  Brefeld  has  shown  with  Ustilago  cruenta  on  a 
similar  host  that  the  germs  can  enter  the  very  young  leaves  of 
even  large  plants,  but  can  not  form  the  mycelium  fast  enough  to 
reach  the  growing  tip  before  it  is  cut  off  by  the  maturing  of  the 
tissues. 

In  germination  broom-corn  .shows  a  common  type  among 
grasses — an  epicotyl,  or  sort  of  an  underground  internode,  is 
formed  connected  at  one  end  with  the  seed  and  at  the  other  bear- 
ing the  leaf-sheath  with  the  enclosed  young  leaves  and  growing 
tips.  The  epicotyl  usually  lengthens  enough  to  bring  the  leaf- 
sheath  above  ground,  and  about  this  time  the  growth  of  the  latter 
is  stopped  so  that  it  is  soon  pierced  at  its  apex  by  the  growing 
leaves  within.  Young  plants  upon  the  seed  of  which  spores  were 
placed  before  germination,  after  they  had  produced  plants  of 
the  above  or  a  little  later  stage,  were  frequently  examined  for 
mycelium  ;  when  this  was  found  it  was  most  abundant  at  the  junc- 
ture of  the  epicotyl  and  leaf-sheath,  and  rarely  extended  very 
far  down  into  the  epicotyl.  Plants  at.  this  age  also  became  in- 
fected when  the  leaf-sheath  was  removed  and  spores  placed  on 
the  young  leaves  at  its  base,  but  did  not  become  infected  when 
the  spores  were  merely  placed  on  the  outside  of  the  base  of  the 
leaf-sheath.  The  direction  of  the  mycelium  in  all  these  cases 
was  chiefly  toward  the  center  of  the  plant  and  up.  As  this  (region 
near  juncture  of  epicotyl  and  leaf-sheath)  is  the  shortest  path 
through  the  plant  tissues  to  the  growing  apex,  it  is  the  most  cer- 
tain and  probably  the  most  common  place  for  successful  infection, 
and  the  earlier  the  threads  enter  the  more  certain  they  are  to 
reach  the  growing  tip.  After  entering  it  is  quite  likely  that  the 
threads  spread  in  all  directions,  if  there  is  no  difference  in  resist- 
ance ;  but  the  maturing  cells  gradually  limit  this  until  finally 
only  the  mycelium  that  has  reached  the  young  growing  parts 
keeps  up  a  vigorous  growth. 

Mycelium.  When  once  the  infection-threads  succeed  in  enter- 
ing the  plant  at  the  proper  place  and  time,  their  further  growth  is 
assured  by  the  nourishment  that  is  taken  from  the  plant,  and  so 
they  soon  become  independent  of  the  sporidia  or  spores  to  which 
they  are  attached  on  the  outside.  They  rapidly  grow  into  long, 
irregularly  branched,  colorless  and  thin  walled  threads  that  ramify 
through  the  tissue  of  the  plant.  The  diameter  of  these  threads 
(2-4  microns)  is  considerably  enlarged  from  that  of  the  infection- 
thread,  whose  very  small  diameter  is  more  favorable  for  penetration 


f$9?.]  BROOM-CORN   SMUT.  385 

of  the  epidermal  cells.  These  threads  now  constitute  the  mycelium 
of  the  fungus.  This  is  not  confined  to  the  intercellular  spaces  but 
runs  as  readily  through  the  cells.  It  is  found  most  abundantly  in 
patches  in  the  parenchyma  cells  which  in  the  epicotyl  form  a  band 
several  cells  deep  surrounding  a  central  cylinder  of  the  wood  cells. 
At  the  juncture  of  the  leaf-sheath  where  the  central  cylinder 
begins  to  separate  into  the  distinct  bundles,  the  mycelial  threads 
run  into  the  parenchyma  cells  surrounding  the  bundles.  They 
were  also  found  in  the  base  of  the  leaf-sheath  and  in  the  lower 
parts  of  the  first  leaves. 

At  first  the  threads  are  filled  with  protoplasm,  but  as  they 
become  older  this  is  more  or  less  lost,  and  septa  are  found  at 
irregular  intervals;  frequently  the  cell  walls  are  swollen  or  the 
contents  so  changed  that  the  lumen  of  the  thread  is  not  distinctly 
made  out.  In  the  older  infected  parts  there  is  frequently  some 
discoloration  of  the  threads  and  of  the  surrounding  plant  cells,  but 
in  parts  but  newly  infested  there  is  no  disturbing  condition  shown. 
As  these  threads  penetrate  further  in  the  plant  they  become  more 
limited  to  the  intercellular  spaces,  and  the  branches  that  penetrate 
into  the  cells  for  nourishment  assume  more  of  a  special  appear- 
ance (pi.  4,  fig.  5).  Reaching  the  young  pith  cells  a  short  distance 
below  the  growing  point  as  new  cells  are  formed  they  gradually 
become  infested  and  thus  the  fungus  follows  the  upward  growth 
of  the  plant  during  the  entire  season.  After  an  infected  plant  has 
made  its  full  growth,  the  mycelium  can  often  be  found  scattered 
through  the  pith  in  the  various  internodes  generally  most  abundant 
in  the  region  of  the  nodes.  Thus  mycelium  has  been  found  in  the 
very  base  and  in  the  very  apex  of  plants,  a  distance  of  eight  or 
ten  feet  apart.  It  is  very  improbable,  however,  that  there  is  a 
continuous  connection  of  the  mycelium  for  even  any  great  part  of 
this  distance,  for  according  to  Brefeld,  the  lengthening  of  the 
internodes  tends  to  destroy  the  continuity  of  the  threads.  It  is 
always  only  the  mycelium  in  the  vicinity  of  the  tip  of  the  plant 
that  is  the  active  growing  part  of  the  fungus. 

Spore  formation.  Such  is  the  history  of  the  fungus  until  the 
time  the  broom-corn  begins  to  form  its  flower  parts,  and  all  this 
time  the  infected  plant,  so  far  as  appearance  goes,  is  similar  to 
the  one  that  is  not  infected.  The  mycelium  penetrates  the  young 
ovaries  and  stamens  usually  before  they  are  very  much  differen- 
tiated. If  this  penetration  is  very  early,  then  the  stamens  and 
ovary  are  not  differentiated  from  each  other  in  the  smutted  body ; 
but  if  the  fungus  has  been  backward  in  its  penetration,  then  the 
smutted  part  shows  ovary  and  stamens  more  or  less  grown  together 
but  still  so  that  they  can  easily  be  made  out  as  these  organs; 


386  BULLETIN  NO.  47.  [March, 

occasionally  the  penetration  is  even  so  late  that  the  stamens  are 
free  from  the  spores,  only  the  ovary  containing  them.  Flowers 
of  an  infected  plant  were  examined  that  were  so  young  that  the 
stamens  and  ovary  showed  only  as  small  undifferentiated  out- 
growths of  cells  from  the  growing  point,  and  while  no  mycelium 
was  definitely  made  out  in  these,  still  it  was  found  among  the 
young  cells  in  their  vicinity,  thus  indicating  that  entrance  of  the 
threads  may  take  place  very  early  in  the  formation  of  the  essential 
organs  of  the  flower.  It  is  also  a  fact  that  by  the  time  the  flower 
parts  are  thrust  into  sight  from  the  enfolding  bases  of  the  leaves 
the  smut  spores  are  in  part  fully  developed  and  apparently  ready 
for  germination. 

Unfortunately  specimens  showing  the  condition  of  the  fungus 
after  penetration  of  the  essential  organs  but  before  spore  forma- 
tion were  not  preserved  for  examination,  and  so  peculiarities  of 
the  mycelium,  if  such  exist,  immediately  preceding  spore  forma- 
tion can  not  be  given  here.  However,  examination  of  the  very 
young  spore  bearing  bodies,  before  all  the  mycelium  has  been 
changed  into  spores,  has  given  information  concerning  some  very 
interesting  changes  that  take  place  in  spore  formation,  and  shows 
that  in  this  species  it  is  quite  different  from  that  attributed  to 
Ustilago  as  a  genus. 

Evidently,  after  entrance  into  the  essential  organs,  the  forma- 
tion of  mycelium  soon  takes  place  most  abundantly  in  the  cells 
immediately  beneath  the  epidermis,  so  that  in  time  this  becomes 
separated  from  the  rest  of  the  plant  cells  by  a  dense  mass  of  fun- 
gous threads,  which,  as  they  multiply  and  change  into  spores, 
crowd  inward  the  inclosed  cells  and  stretch  outward  the  layer  of 
epidermal  cells,  the  final  result  being  the  seed-like  smutted  part 
with  its  membrane  on  the  outside,  mass  of  spores  within,  and  the 
columella  in  the  center. 

Sections  through  these  infected  bodies  while  quite  young 
show  the  origin  and  character  of  these  parts.  Taking  first  the 
columella  we  find  that  it  narrows  somewhat  irregularly  from  the 
base  toward  the  apex  and  terminates  before  reaching  the  end  of 
the  spore  bearing  body.  It  forms  a  stiff,  slender  column  that 
remains  after  the  rest  of  the  body  has  crumbled  to  pieces.  If 
stamens  go  to  make  up  part  of  the  infected  body  but  are  made 
out  as  free  bodies  at  the  apex,  the  columella  will  send  out  a  little 
branch  into  each  of  these  originating  from  below  where  the  stamen 
loses  its  identity  with  the  main  body ;  or  if  the  stamens  are 
entirely  free  from  the  ovary  but  still  infected  each  will  have  its 
own  columella.  These  columellas  evidently  are  thus  the  fibro- 
vascular  parts  and  the  undestroyed  parenchyma  cells  that  were 


1897.}  BROOM-CORN   SMUT.  387 

intended  for  the  formation  of  the  essential  organs  of  the  flower. 
In  stained  sections  they  plainly  show  considerable  of  the  sterile 
fungous  threads  ramifying  through  them. 

Proceeding  now  to  the  membrane  on  the  outside,  the  micro- 
scope shows  that  it  is  not  entirely  made  up  of  the  epidermal  cells, 
but  is  rather  a  false  membrane  having  on  the  outside  the  still  more 
or  less  distinct  epidermis,  but  beneath  this  a  tissue  of  sterile  fun- 
gous threads  which  forms  its  greater  thickness.  These  sterile 
threads  are  quite  different  from  the  usual  threads  of  the  mycelium, 
especially  when  fully  matured,  and  exhibit  some  variations  in 
the  hosts  that  belong  to  varieties  other  than- broom-corn.  The 
threads  tend  to  break  up  into  their  component  cells  or  short  rows 
of  these.  The  cells  become  rounded  at  their  ends  and  assume  a 
sub-spherical  to  irregular  oblong  shape.  The  walls  are  more  or 
less  thickened.  Though  usually  empty  they  may  contain  some 
contents.  The  cell  walls  always  retain  their  hyaline  appearance 
and  because  of  this  and  their  large  size  and  grouping  together  are 
in  no  way  likely  to  be  confused  with  the  fertile  spores  that  occur 
just  beneath  this  membrane. 

The  sections  also  show  that  the  spores  are  not  formed  simul- 
taneously from  the  fertile  threads  that  exist  between  the  envelop- 
ing sterile  cells  of  the  membrane  and  the  central  plant  cells  of  the 
columella,  but  that  there  is  a  progressive  formation  from  without 
toward  the  columella  or  centripetally.  It  is  quite  probable,  too, 
that  this  formation  begins  first  at  the  free  end,  so  that  the  oldest 
spores  would  be  those  near  the  top  of  the  infected  body.  The 
formation  of  the  spores  so  far  as  could  be  gathered  from  the 
youngest  specimens  at  hand  was  as  follows.  Beginning  next  the 
columella  the  section  presents  an  appearance  as  if  the  fungous 
threads  had  entirely  gelatinized  their  walls,  which,  with  the  dis- 
solved cell  contents,  formed  a  colorless  amorphous  stratum  in 
which  were  imbedded  the  protoplasmic  contents  as  very  distinct, 
narrow  and  usually  short  and  simple  strands,  almost  bacteria-like 
in  appearance.  In  these  fine  strands,  less  than  a  micron  in  diam- 
eter, are  to  be  made  out  more  highly  refractive  granules,  possibly 
nuclear  functioning  bodies.  As  we  proceed  outward  in  the  section 
the  strands  become  irregularly  contracted  and  apparently  larger 
until  we  meet  with  those  that  are  roundish  and  reforming  a  visible 
cell  wall.  Further  out  in  the  section  the  cell  wall  is  more  dis- 
tinctly made  out  and  becomes  tinted.  From  here  they  grade  into 
spores  that  are  fully  developed  as  to  size,  shape  and  color  but  are 
bound  very  closely  together,  while  the  outermost  spores  do  not 
so  firmly  adhere  to  one  another.  The  transformation  is  generally 
gradual,  there  being  no  sharp  line  of  separation,  that  of  color 
being  most  marked.  There  is  more  or  less  of  a  radial  effect  in 


388  BULLETIN  NO.  47.  [Marc /t, 

the  undeveloped  parts,  as  if  the  formation  was  not  entirely  annu- 
lar but  as  if  various  radial  units  had  given  origin  to  the  formation 
but  had  more  or  less  lost  their  individuality  by  lateral  fusion. 
Perhaps  projecting  wedges  of  plant  tissue  give  rise  to  this 
effect  in  part,  but  where  these  are  apparently  absent  there  are  seen 
radial  strands  where  the  gelatinization  of  walls,  etc.,  are  not  so 
marked.  In  the  above  manner  gradually  all  of  the  spores  are 
matured.  When  this  has  occurred,  the  spore  mass  dries  out  and 
becomes  dusty,  and  the  enveloping  membrane  sooner  or  later 
becomes  ruptured  and  the  spores  are  easily  scattered  by  the  wind. 
From  the  abov^description  it  is  seen  that  the  spore  formation 
is  quite  different  from  that  usually  described  for  Ustilago.  How- 
ever, an  examination  of  very  young  outbreaks  of  Ustilago  Zeae 
(Beckm.)  Unger  in  the  leaves  of  corn  showed  that  there  is  con- 
siderable resemblance.  Here  I  found  that  frequently  small  groups 
of  spores  were  formed  from  a  mass  of  mycelium  encircled  on  all 
sides  by  plant  cells  ;  and,  while  there  was  a  less  decided  geletiniza- 
tion  of  walls  and  re-arrangement  of  protoplasmic  strands,  there 
was  still  a  progression  of  spore  development,  though  it  was  not 
nearly  so  marked  as  in  broom-corn  smut,  and  the  central  spores 
seemed  to  be  the  ones  first  formed.  There  were  also  threads  more 
isolated  in  the  plant  tissue  that  were  forming  spores  after  the 
manner  usually  described  for  this  genus.  On  the  other  hand  an 
examination  of  Cintractia  as  described  by  Cornu1  and  Trelease,2  and 
as  exhibited  by  sections  through  rather  mature  specimens  of 
Cintractia  axicola  and  Cintractia  Junci  (species  with  which  the 
above  authors  worked)  shows  that  the  fungus  on  broom-corn  is  a 
Cintractia,  if  that  is  entitled  to  generic  distinction  from  Ustilago. 
In  both  of  these  species,  as  we  found  with  broom-corn,  there  is  a 
membrane  composed  of  sterile  cells  and  epidermis,  but  with  them, 
unlike  in  broom-corn,  the  outbreak  occurs  just  beneath  the  epi- 
dermis at  the  base  of  the  flower  peduncles;  and,  as  the  enclosed 
woody  portion  is  normally  developed,  the  strain  of  the  spore 
formation  of  necessity  ruptures  the  surrounding  membrane  and  it 
soon  falls  off,  leaving  the  spores  naked  but  more  or  less  agglu- 
tinated. These  have  been  developed  centripetally  around  the 
central  cylinder  of  plant  tissue,  similarly  to  those  of  broom-corn 
smut  around  the  columella.  In  Cintractia  axicola  there  is  also 
the  radial  effect  but  shown  much  more  prominently.  The  germi- 
nation of  Cintractia  Junci  is  somewhat  similar,  at  least  in  water, 
to  that  of  broom-corn  smut.  The  place  of  outbreak  and  the 
appearance  of  the  spores,  however,  in  both  these  species  is  dif- 
ferent from  those  of  broom-corn. 

'Ann.  Sci.  Nat.  Bot   VI.  15:  277-279.     1883. 
"Bull.  Torr.  Bot.  Club  12.  69-70.     Jl.  1885. 


1897.]  BROOM-CORN   SMUT.  389 

EXPERIMENTS. 

Object.  To  determine  some  of  the  preceding  facts  concern- 
ing the  life  history  of  the  fungus  and  also  to  find  out  whether  it 
was  a  trouble  that  could  be  prevented,  it  was  necessary  to  carry 
on  a  number  of  experiments  with  plants  both  in  the  laboratory  and 
in  the  field.  The  indoor  experiments  were  along  two  lines.  First, 
to  determine  by  infection  the  place  or  places  on  the  broom-corn 
through  which  the  smut  gains  entrance.  Second,  to  determine 
the  effect  of  hot  water  on  the  germination  of  the  seeds  of  broom- 
corn  and  of  the  spores  of  the  fungus.  The  field  experiments 
were  chiefly  to  compare  the  amount  of  smut  produced  in  plants 
whose  seed  was  treated  with  hot  water  with  that  produced  in 
those  whose  seed  was  not  treated. 

Infection  experiments.  While  many  attempts  were  made  to 
infect  plants  by  placing  spores  on  the  seed  or  on  very  young 
parts  of  the  germinating  plants,  the  success  of  which  was  deter- 
mined later  by  the  presence  of  mycelium  in  the  tissues,  the  per 
cent,  of  plants  that  became  infected  was  not  very  large.  This  was 
doubtless  due  in  part  to  the  use  of  spores,  instead  of  pure  cultures 
of  sporidia  of  the  right  age  for  infection — the  method  used  by 
Brefeld.  The  spores,  however,  always  germinated  very  easily  and 
abundantly,  and  it  was  thought  they  would  furnish  a  source  for 
infection  equal  to  that  which  exists  in  nature.  The  spores  were 
used  also  to  determine,  if  possible,  whether  the  fine  threads  of 
the  spores  that  we  have  called  infection-threads  were  really  of 
that  nature.  The  experiments  were  mostly  made  with  seed  treated 
with  hot  water,  and  germinated  in  soil  or  sand  free  from  spores. 
The  germinating  seeds  were  then  moistened  at  certain  places,  or 
at  certain  ages,  with  water  containing  spores.  After  growth  vary- 
ing from  a  day  or  so  to  two  or  three  weeks  either  the  epidermis 
was  examined  for  evidences  of  penetration  or  sections  were  cut 
and  examined  for  mycelium. 

It  seems  to  be  a  fact  that  there  is  a  close  relationship  between 
the  stage  of  germination  of  the  spores  and  the  place  or  age  of  the 
parts  through  which  infection  takes  place.  These  conditions 
seemed  to  be  best  adjusted  by  placing  the  spores  on  the  seed  and 
allowing  both  to  germinate  together  in  earth,  at  least  most  of  the 
plants  that  became  infested  were  those  so  treated.  Although  many 
trials  were  made  by  placing  germinated  or  ungerminated  spores 
on  the  germs  at  various  places  and  ages,  we  were  not  successful  in 
our  examination  of  the  epidermis  afterward  in  finding  spores  or 
sporidia  on  the  outside  that  were  connected  with  mycelium 
within.  It  was  a  common  thing,  however,  to  find  vigorously  ger- 
minating spores  in  which  there  were  no  signs  of  the  threads  pene- 


390  BULLETIN  NO.  47.  \March, 

trating  the  epidermis.  A  few  spores  were  found  in  one  case 
where  there  seemed  to  be  some  attempt  on  the  part  of  the  infec- 
tion-threads to  push  down  between  the  cell  walls  of  the  epidermis. 
Mycelium,  in  the  sections,  was  frequently  found  in  the  epidermal 
cells,  in  a  few  cases  showing  a  narrowed  part  at  the  end  of  a 
thread  as  if  entrance  had  been  gained  near  that  point  (pi.  4,  fig.  3). 
The  mycelium  was  always  most  abundant  in  the  region  where 
epicotyl  and  leaf-sheath  joined,  and  very  little,  if  any,  toward  the 
seed  end  of  the  epicotyl.  This  would  seem  to  indicate,  at  least  in 
these  cases,  that  if  penetration  took  place  through  the  epicotyl  it 
did  so  very  early,  or  only  at  the  upper  end  if  later.  That  it  is 
largely  a  question  of  young  tissue  that  can  be  penetrated  easily  is 
shown  by  the  fact  that  plants  that  had  one  or  two  leaves  through 
the  sheath,  but  with  this  still  fresh,  became  infected  when  this  was 
removed  and  spores  placed  on  the  base  of  the  exposed  leaves 
where  the  cells  were  quite  young;  while  plants  not  nearly  so  old 
did  not  become  infected  when  spores  were  merely  placed  at  a 
corresponding  position  but  on  the  outside  of  the  normally  exposed 
parts  of  the  sheath,  the  cells  there  being  more  mature.  In  the 
field  experiments  where  spores  were  placed  on  young  leaves  at 
different  ages  of  the  plants,  it  was  shown  that  successful  infection 
did  not  take  place  in  these  cases,  probably,  because  even  if  pene- 
tration was  successful,  the  threads  were  not  able  to  reach  the 
growing  tip. 

Effect  of  treatment  on  seed.  In  the  treatment  with  hot  water  it 
was  desired  to  find  out  at  what  temperature  the  treatment  began 
to  injure  the  germinative  power  of  the  seeds,  how  much  higher 
this  temperature  is  than  that  at  which  the  spores  are  killed,  and 
whether  this  difference,  if  any,  was  great  enough  to  permit  of  the 
.treatment  as  a  practical  operation.  Two  vessels  of  water  were 
used — one  at  about  the  required  temperature  in  which  the  seeds 
in  a  small  bag  were  placed  to  take  off  the  chill,  and  the  other  at 
the  desired  constant  temperature,  in  which  the  seeds  were  im- 
mersed for  the  required  time.  The  thermometer  was  placed  in- 
side the  bag  so  that  it  would  register  the  temperature  of  the 
water  immediately  surrounding  the  seeds.  After  treatment  one 
hundred  seeds  were  selected  and,  with  a  similar  number  of  un- 
treated as  a  check,  were  placed  in  a  Geneva  germinator.  Every 
twenty-four  hours  all  seeds  that  had  germinated  were  removed 
and  the  number  noted. 

In  the  following  table  the  results  of  the  treatments  are  given. 
In  some  cases  the  same  treatment  was  tried  twice  but  at  different 
times  of  the  year.  The  different  lots  were  treated  at  various 
times  during  the  fall  and  winter  and  germinated  in  a  room  where 


BROOM-CORN  SMUT. 


391 


there  was  some  variation  of  temperature.  The  conditions  for 
each  treated  lot  and  its  check  were,  however,  exactly  the  same. 
From  the  table  it  will  be  seen  that  there  was  practically  no  differ- 
ence between  the  treated  and  untreated  lots  up  to  the  tempera- 
ture of  132°  F.,  and  135°  F.  for  ten  minutes.  From  here  on  there 
was  somewhat  of  a  retardation  of  germination.  The  treatment 
at  140°  F.  and  higher  seems  on  some  occasions  also  to  have  killed 
some  few  seeds.  These  results,  of  course,  might  vary  with  the 
seed  used — the  older  the  seed  the  less  likely  it  would  be  to  stand 
the  higher  temperatures;  different  varieties  might  vary  slightly 
in  resistance  power;  seeds  freed  from  their  glumes  would  be  in- 
jured more  easily  than  seed  tightly  invested  by  the  glumes.  The 
results,  however,  show  that  broom-corn  seed  has  a  resistance 
power  against  hot  water  higher  than  that  of  our  other  common 
agricultural  grasses,  and  consequently  there  would  be  less  chance 
of  injury  to  the  seed  in  the  treatment,  other  conditions  being  the 
same 

GERMINATION  OF  BROOM-CORN  SEED  TREATED  WITH  HOT  WATER. 


Treatment  of  seeds. 

Hours  after  placing  in  germinator. 

O 
n 

3 

%  failed. 

24 

48 

72 

96 

1  20 

144 

1  68 

192 

216 

240 

264 

Seeds  in  hot  water,  120° 
F  for  15  min  

Treated 
Check 

o 

o 

13 

II 

47 
61 

21 
19 

5 

i 

6 
o 

5 
4 

97 
96 

3 
4 

Seeds  in  hot  water,  130° 
F.  for  5  min  

Treated 
Check 

2 

4 

8 

IO 

63 
64 

14 

12 

2 
2 

2 
2 

4 

2 

95 
96 

5 
4 

Seeds  in  hot  water,  130° 
F.  for  10  min  

Treated 
Check 

i 

0 

5 
6 

76 

82 

8 

5 

3 
O 

I 

3 

2 
2 

96 
98 

4 

2 

Seeds  in  hot  water,  130° 
F  for  1  5  min   

Treated 
Check 

3 

I 

7 

2 

60 

55 

18 
37 

9 
i 

5 

96 
96 

4 
4 

Seeds  in  hot  water,  130° 
F.  for  1  5  min  

Treated 
Check 

o 
o 

8 
8 

30 
36 

28 
30 

13 
13 

2 
2 

2 

2 

I 

2 

3 

2 

95 

IOO 

5 
o 

Seeds  in  hot  water,  132° 
F  for  5  min   .  .  . 

Treated 
Check 

I 
o 

18 
23 

50 

23 

18 

3 

2 

95 
94 

5 
6 

Seeds  in  hot  water,  132° 
F  for  lo  min   .... 

Treated 
Check 

0 
0 

8 
29 

44 
34 

24 

22 

14 

5 

7 
7 

O 

I 

i 

i 

98 
99 

2 
I 

Seeds  in  hot  water,  135° 
F.  for  5  min  

Treated 
Check 

o 
I 

12 

16 

33 
34 

24 
19 

19 
14 

6 

5 

3 
i 

i 
o 

2 
3 

2 

IOO 

95 

0 

5 

Seeds  in  hot  water,  135° 
F.  for  10  min  

Treated 
Check 

o 
o 

2 
17 

33 

37 

27 

25 

18 
6 

3 
6 

5 
o 

3 
o 

2 
I 

93 
92 

7 

8 

Seeds  in  hot  water,  135° 
F.  for  1  5  min  

Treated 
Check 

3 
3 

50 
67 

25 

12 

1 

5 

5 

5 
i 

i 
i 

99 
96 

i 

4 

Seeds  in  hot  water,  135° 
F.  for  1  5  min  

Treated 
Check 

i 
o 

5 
8 

34 
51 

26 
24 

13 

12 

8 
5 

5 
o 

I 
O 

2 

O 

I 

96 

IOO 

4 

0 

Seeds  in  hot  water,  140° 
F.  for  1  5  min  

Treated 
Check 

2 

3 

12 
67 

23 

12 

17 

7 

IO 

5 

9 
i 

4 
i 

77 
96 

23 
4 

Seeds  in  hot  water,  150° 
F.  for  15  min.      ... 

Treated 
Check 

I 
II 

o 
o 

28 
60 

2 

6 

22 

43 

41 
17 

23 

ii 

7 

5 

2 

25 
17 

2 
I 

5 

3 
o 

O 
2 

2 
0 

88 

95 
97 

12 
2 

5 

Seeds  in  hot  water,  150° 
F.  for  15  min  

Treated 
Check 

2 
I 

392  BULLETIN  NO.  47.  {March, 

Effect  of  treatment  on  spores.  The  effect  of  hot  water  on  the 
germination  of  the  spores  was  studied  at  the  same  time.  Smutted 
seed-like  bodies  (broken  and  entire)  were  placed  with  the  seed  to 
be  treated,  also  spores  placed  on  the  inner  surface  of  a  small  piece 
of  paper  that  was  folded  once.  In  the  last  case  the  spores  were 
placed  on  the  paper  in  order  that  they  could  be  found  after  treat- 
ment, and  were  supposed  to  be  subjected  to  the  same  temperature 
as  spores  that  might  occur  on  the  surface  of  seeds.  Possibly  the 
paper  furnished  some  little  protection  against  the  heat,  but  cer- 
tainly not  so  much  as  would  be  furnished  those  spores  that  had 
slipped  down  between  the  glumes  of  the  seeds.  After  treatment 
some  of  the  spores  from  the  interior  of  unbroken  smutted  bodies, 
from  the  broken  ones  and  from  the  paper,  together  with  untreated 
spore  as  a  check,  were  placed  in  water  in  culture  cells  and  exam- 
ined with  the  microscope  from  time  to  time  to  determine  the 
amount  and  time  of  their  germination.  The  results,  abbreviated 
from  the  notes  taken  at  the  time,  are  as  follows : 

No.  1028.  In  hot  water  130°  F.  for  5  min.;  spores  taken  from  inside  of  unbroken 
body.  Examined  17  hours  after  placing  in  culture  cells,  and  found  spores  germinating 
very  actively,  probably  from  50  to  75  per  cent.;  stage  of  germination  possibly  not  quite 
so  far  advanced  as  in  the  check. 

No.  1029.  Treatment  same  ;  spores  from  surface  of  paper.  Examined  same  time  as 
above,  and  found  not  over  one  or  two  per  cent,  germinating  and  these  much  behind 
stage  of  development  of  those  in  the  check. 

No.  1030.  Check,  or  spores  not  treated.  When  examined  with  above  found  nearly 
every  spore  germinating  and  most  of  them  quite  far  advanced. 

Later  examination  showed  little  change  in  the  relative  amounts  of  germination  of  the 
above. 

No.  1035.  In  hot  water  130°  F.  for  10  min.;  spores  from  inside  of  unbroken  body. 
Examined  24  hours  after  placing  in  culture  cells,  and  found  about  5  per  cent,  had  germ- 
inated and  these  in  about  the  same  stage  as  check  spores.  .  - 

No.  1034.  Treatment  same;  spores  from  surface  of  paper.  At  end  of  24  hours 
about  3  per  cent,  had  germinated  and  these  were  not  so  far  advanced  as  in  check. 

No.  1036.     Check.     About  50  per  cent,  had  germinated  and  these  well  advanced. 

Have  no  data  as  to  later  examinations  and  conditions. 

No.  1045.  In  hot  water  132°  F.  for  10  min.;  spores  from  inside  of  body.  Exam- 
ined 24  hours  after  placing  in  culture  cells  and  found  less  than  a  dozen  germinating 
spores.  At  end  of  48  hours,  however,  the  spores  had  germinated  abundantly,  though  not 
so  abundantly  as  in  check.  A  second  culture  made  24  hours  after  treatment  and  taken 
from  a  different  infected  body  that  had  quite  a  tough  and  unbroken  membrane  showed 
no  retardation  in  germination  at  the  end  of  24  hours,  and  also  had  about  as  many  spores 
germinating  as  in  the  check  lot. 

No.  1044.  Treatment  same ;  spores  from  surface  of  paper.  Results  the  same  as  in 
first  example  of  1045. 

No.  1046.  Check.  At  end  of  24  hours  germinated  spores  were  very  abundant  and 
very  well  advanced. 

No.  1049.  In  hot  water  I34°-50  F.  for  5  min.;  spores  from  inside  of  an  unbroken  and 
firmly  covered  body.  Examined  at  end  of  24  hours  and  found  germination  well  ad- 
vanced, and  even  more  abundant  than  in  check  slide. 


BROOM-CORN  SMUT.  393 

No.  1048.  Treatment  same ;  spores  from  surface  of  paper.  At  end  of  24  hours  only 
a  spore  or  two  had  germinated;  at  end  of  48  hours  a  few  more  had  germinated;  at  end 
of  65  hours  quite  a  few  extra  were  beginning  to  germinate,  though  altogether  not  over  5 
or  10  per  cent. 

No.  1050.  Check.  At  end  of  24  hours  germination  was  abundant,  though  perhaps 
exceeded  in  1049. 

No.  1051.  In  hot  water  135°  F.  for  10  min.;  spores  from  center  of  unbroken  body. 
At  end  of  24  hours  examined  and  found  the  spores  were  germinating  as  well  in  all  re- 
spects as  in  check.  The  covering  of  the  infected  body  had  protected  these  central  spores 
so  that  they  had  not  become  wet,  and  the  treatment  if  anything  had  done  them  good. 

No.  1052.  Treatment  same ;  spores  from  the  same  body  but  near  the  surface.  These 
spores  had  been  wet  by  the  water,  and  while  their  germination  was  retarded  somewhat 
and  was  not  so  abundant  as  the  above,  it  was  still  quite  vigorous. 

No.  1053.  Treatment  same  ;  spores  from  surface  of  paper.  At  end  of  24  hours  less 
than  a  dozen  spores  had  germinated  out  of  the  many  hundreds  present. 

No.  1054.  Treatment  same ;  spores  from  inside  a  punctured  body.  At  end  of  24 
hours  did  not  find  any  germinating  spores.  Later  on  about  a  dozen  germinating  spores 
were  found. 

No.  1055.  Check.  At  end  of  24  hours  the  spores  had  germinated  very  abundantly; 
condition  about  as  in  1051. 

At  end  of  four  days  the  per  cent,  of  germination  in  the  above  had  not  increased  to 
any  appreciable  extent. 

No.  1103.  In  hot  water  135°  F.  for  15  min.;  spores  from  center  of  an  unbroken 
body.  Examined  at  end  of  24  hours  and  found  the  spores  had  begun  to  germinate 
abundantly. 

No.  1102.  Treatment  same;  spores  from  surface  of  paper.  None  of  these  spores 
germinated. 

This  experiment  was  tried  twice  with  abwt  the  same  results.  A  nutrient  fluid  was 
used  as  the  medium  in  this  case. 

No.  1107.  In  hot  water  150°  F.  for  15  ,_iin.,  ipores  from  center  of  unbroken  seed. 
No  spores  germinated. 

No.  1106.     Treatment  same;  spores  from  .  arfaceof  paper.     No  spores  germinated. 

These  experiments  show  that  a  short  treatment  with  warm 
water  has  no  injurious  effect,  may  possibly  even  be  beneficial  to 
the  germination  of  the  spores.  As  the  temperature  of  the  water 
is  increased,  however,  it  shows  a  retarding  influence  on  the  germi- 
nation. Closely  associated  with  retarded  development  is  the  fatal 
effect  of  the  hot  water.  In  general,  a  direct  exposure  in  water  at 
I30°-I32°  F.  for  five  or  ten  minutes  showed  a  retarding  and  with 
some  spores  a  fatal  effect.  A  direct  exposure  for  fifteen  minutes 
in  water  at  135°  F.  is  almost  certain  to  prove  fatal  to  all  of  the 
spores.  Spores,  however,  in  the  unbroken  bodies  can  stand 
immersion  in  water  of  a  higher  temperature,  the  degree  depend- 
ing upon  the  thickness  or  impenetrability  of  the  membrane  to 
the  water. 

It  was  shown  in  the  treatment  of  broom-corn  seed  that  an 
exposure  at  140°  F.  for  fifteen  minutes  may  be  taken  as  the  lower 
limit  at  which  we  may  begin  to  look  for  bad  effects  from  the  treat- 


394  BULLETIN  NO.  47.  [March, 

ment  of  good  seed.  This  gives  a  greater  safety  range  than  we 
have  in  the  similar  treatment  for  the  smut  of  oats  or  wheat.  Per- 
fect results  in  preventing  the  smut  can  not  always  be  expected 
with  seed  in  which  there  are  many  unbroken  infected  kernels, 
as  the  treatment  (135°  F.  for  fifteen  minutes)  will  not  be  severe 
enough  to  kill  all  of  the  spores,  and  subsequent  handling  may 
break  the  kernels  and  scatter  the  spores  among  the  seed.  It  is 
quite  possible,  also,  that  spores  that  have  worked  down  between 
the  glumes  are  sometimes  protected  sufficiently  to  withstand  this 
treatment  and  are  able  to  infect  the  germinating  plant.  These 
conditions  probably  account  for  the  imperfect  results  obtained  in 
some  of  the  following  experiments  where  a  large  amount  of  smut 
was  mixed  with  the  seed  before  treatment. 

At  the  same  time  th'at  the  heat  experiments  were  conducted  a 
few  were  tried  to  determine  the  influence  of  cold.  Are  the  con- 
ditions of  winter  weather  such  as  would  kill  spores  in  infected 
canes  left  outdoors  on  the  ground  ?  The  germination  of  some 
spores  that  had  been  so  treated  was  tried  in  the  spring.  Only  one 
trial  was  made  but  this  failed  to  show  any  germinating  spores. 
However,  they  all  presented  the  appearance  as  if  they  had  germi- 
nated before,  which  was  quite  likely  the  case.  The  germination 
of  spores  subjected  to  the  following  conditions  was  also  tried : 

No.  1060.     Spores  on  ice  for  15  minutes. 

No.  1061.     Check  culture. 

No.  1062.     Spores  on  ice  for  one  hour. 

No.  1063.     Spores  in  ice-water  for  four  hours. 
At  the  end  of  24  hours  after   placing  in  culture  cells,  all  the 
above  had  germinated  abundantly,  showing  no  difference  at  that 
time  or  later. 

Field  experiments,  1894..  During  this  year  experiments  were 
first  undertaken  to  prevent  broom-corn  from  smutting.  Two  lots 
of  seed,  one  ordinary  seed  and  the  other  quite  smutty,  were  di- 
vided into  three  parts,  a  treatment  with  hot  water  and  with  a  solu- 
tion of  copper  sulphate  being  given  to  two  of  the  parts  of  each 
lot  and  the  third  parts  left  untreated.  The  seed,  however,  was 
planted  so  late  that  the  broom-corn  did  not  have  time  to  com- 
pletely form  its  panicles  before  it  was  killed  by  frost.  A  care- 
ful examination  of  the  immature  panicles  that  had  appeared 
showed  but  three  smutted  ones,  and  those  all  from  the  untreated 
lot  of  badly  smutted  seed.  In  this  plat  one  hundred  twenty-five 
plants  were  advanced  enough  to  examine  the  panicles.  The  con- 
ditions were  not  such  as  to  give  trustworthy  results  and  no  con- 
clusions could  be  had. 


'897-1 


BROOM-CORN   SMUT. 


395 


Field  experiments,  1895.  This  year  the  experiments  were  con- 
siderably widened  so  as  to  include  not  only  experiments  in  pre- 
venting and  increasing  smut  in  the  plants  but  also  one  to  de- 
termine whether  plants  could  become  infected  by  spores  carried 
to  the  tender  parts  above  ground.  The  conditions  and  results  of 
these  experiments  are  given  in  the  table  for  1895.  From  this  it 
will  be  seen  that  experiments  i  and  2  were  conducted  at  Arcola, 
111.,  which  is  in  the  principal  broom-corn  district  of  the  state. 
The  seed,  however,  was  planted  on  land  that  had  not  been  in 
broom-corn  before.  Unfortunately  the  broom-corn  was  cut  a  few 
days  before  the  writer  examined  it,  but  the  smutted  heads  had 
been  left  behind  and  so  could  be  counted,  while  the  total  was 
easily  obtained  from  standing  bases  of  the  canes.  The  remaining 
experiments  were  conducted  at  Urbana,  111.,  out  of  the  broom- 
corn  district  and  on  land  that  had  never  been  in  broom-corn  be- 
fore. In  all  cases  the  smut  used  was  such  that  germinated  readily 
in  water.  In  the  last  experiment  the  spores  were  in  water  that 
was  squirted  on  the  young  unrolled  parts  when  the  plants  aver- 
aged about  six  inches  high. 

FIELD  EXPERIMENTS  WITH  BROOM-CORN  SMUT,  1895. 


No. 

Conditions  of  the  experiments. 

Smutty. 

Free. 

Total. 

%  Smutty. 

i. 

Seed   mixed   with   smut;  no  treat- 

40 

760 

800 

5. 

2. 

Seed  mixed  with  smut  ;  treated  with 
hot  water  135°  F.  for  15  min.  At 
Arcola  111  .  

2 

708 

800 

O.25 

Ordinary  seed  ;  no  treatment  

20 

118^ 

1  201 

1.66 

4- 

Seed  mixed  with  smut;  no  treatment. 

126 

1074 

1  200 

10.5 

5- 

Seed  treated  with  hot  water  135°  F. 
for  15  min.;  mixed  with  smut  two 
years  old  

174 

1072 

1246 

14. 

6. 

Seed  mixed  with  smut;  treated  with 
hot  water  135°  F.  for  15  min  

2 

927 

929 

0.21 

7- 

Seed  mixed  with  smut;  treated  with 
hot  water  140°  F.  for  15  min  

I 

1320 

1321 

0.07 

8. 

Seed  mixed  with  smut;  placed  in 
water  to  skim  off  smutted  kernels; 
treated  with  hot  water  135°  F.  for 
1  5  min  

o 

1168 

fi  68 

O. 

9- 

Seed  treated  with  hot  water  135°  F. 
for  15  min.;  smut  placed  on  young 
plants  soon  after  coming  up  

I 

I3M 

1315 

0.07 

These  experiments  show  that  in  every  case  where  used  the 
hot  water  practically  prevented  the  smut,  no  matter  whether  ordi- 
nary or  very  smutty  seed  had  been  so  treated.  Also  that  whereas 


396  BULLETIN  NO.  47.  [March, 

the  ordinary  seed  gave  less  than  2  per  cent,  of  smutted  plants, 
this  was. increased  to  10  and  14  per  cent,  when  very  smutty  seed 
was  used  ;  that  smut  two  years  old  which  had  been  kept  in  a  dry 
place  had  lost  none  of  its  power  to  infect  plants.  Lastly  it  was 
shown  that  smut  in  these  plants  was  not  increased  by  spores  being 
placed  on  the  young  parts  above  ground.  Before  drawing  con- 
clusions from  these  experiments,  the  conclusions  from  which 
seemed  so  evident,  it  was  desired  to  repeat  them  another  year, 
and  add  others  suggested  by  them. 

Field  experiments,  1896.  The  experiments  this  year  were  all 
made  at  Urbana,  the  ground  that  had  been  used  the  year  before 
and  a  new  piece  being  had  for  the  two  sets  of  experiments. 
With  the  ground  that  had  been  in  broom-corn  the  previous  year, 
the  aim  was  two-fold.  First,  to  determine  the  relation  of  smut  in 
the  land  to  the  amount  of  smut  in  the  crop ;  and  second,  to  test 
again  the  value  of  hot  water  treatment. 

In  table  I  for  1896  is  given  a  diagram  of  the  way  the  land  was 
platted  during  the  two  years.  The  dark  lines  indicate  the  boundary 
of  the  land.  In  1895  t^e  seven  plats,  3-9,  ran  cross-wise,  while  in 
1896  the  four  plats,  a-d,  extended  lengthwise  of  the  same.  From 
the  table  it  will  be  seen  that  in  1895  plats  4  and  5  bore  by  far  the 
smuttiest  crop  ;  but  as  most  of  the  smutty  panicles  were  removed 
before  much  of  the  smut  was  shed,  there  was  perhaps  not  much 
that  reached  the  ground  in  any  plat.  However,  to  make  a  differ- 
ence, in  the  fall  of  1895  a  large  amount  of  smut  was  dusted  from 
the  panicles  all  over  plat  4  and  the  smutted  panicles  were  placed 
on  this  plat.  There  could  be  no  doubt  that  this  plat  contained  a 
good  deal  of  smut  and  that  at  least  plats  8  and  9  had  very  little  if 
any.  If  smut  in  the  land  was  one  of  the  means  of  infecting  a 
crop,  then  the  plants  in  the  four  plats  of  1896  might  be  expected 
to  show  the  most  smut  where  they  crossed  plat  4  of  1895.  In  the 
table  the  total  number  of  stalks,  the  number  of  smutted  ones,  and 
the  per  cent,  of  smutted  ones  that  were  found  in  the  experiment 
of  1896  are  given  for  each  of  the  areas  formed  by  the  cross  plat- 
ing of  the  two  years.  A  glance  at  this  will  show  that  plat  4  in 
none  of  the  four  treatments  gave  evidence  of  an  increased  per 
cent,  of  smut  over  the  rest  of  the  land  having  seed  treated  the 
same.  This,  taken  with  the  fact  that  in  plat  a,  where  the  seed  was 
treated  and  there  was  no  smut  in  any  of  the  areas,  would  indicate 
that  smutty  land  is  not  an  important  factor  in  producing  a  smutty 
crop. 

The  second  aim  of  the  experiment,  to  determine  the  effect  of 
hot  water  treatment,  is  shown  in  the  column  of  totals  for  the  four 
treatments.  Ordinary  seed  treated  with  hot  water  gave  a  crop 


1897.} 


BROOM-CORN   SMUT. 


397 


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entirely  free  from  smut,  while  the  crop  from  the  same  lot  of  seed 
but  not  treated  had  nearly  three  and  a  half  per  cent,  of  the  pani- 
cles smutted.  In  the  case  where  smut  was  mixed  with  the  seed 


398 


BULLETIN   NO.   47. 


[March, 


the  part  that  was  afterward  treated  with  hot  water  produced  a  crop 
that  only  had  four  and  one-third  per  cent,  of  the  panicles  smutted, 
while  the  untreated  part  gave  a  crop  of  which  twenty-eight  per 
cent,  was  smutted.  The  results  of  treatment,  then,  were  the  same 
as  in  the  previous  year,  save  that  in  the  case  of  the  badly  smutted 
seed  the  prevention  of  smut  was  not  quite  so  complete.  This  can 
be  explained  on  the  assumption  that  the  treatment  was  not  severe 
enough  to  kill  all  the  spores  (spores  in  the  inside  of  smutted  ker- 
nels or  possibly  some  of  those  that  had  slipped  down  between  the 
glumes  of  sound  seed)  and  by  the  fact  that  here  it  was  an  unusu- 
ally good  year  for  the  development  of  smut,  as  is  shown  by  the 
large  amount  given  for  the  plats  of  these  and  the  next  experiments. 
The  second  set  of  experiments  made  in  1896,  as  was  stated, 
was  on  land  that  had  never  before  been  in  broom-corn,  and 
included  beside  the  preventive  experiments  (as  a  check  on  the 
preceding  set)  a  few  to  determine  the  possibility  of  infecting 
young  plants  of  different  ages  by  placing  spores  on  them.  The 
results  are  embodied  in  the  following  table. 

TABLE  2.    FIELD  EXPERIMENTS  WITH   BROOM-CORN,  1896. 


Plat. 

Conditions  of  the  experiments. 

Smutty. 

Free. 

Total. 

Per  cent. 

A. 

Ordinary    seed  ;    treated  with   hot 
water  I33°-I35°  F.  for  15  min.  .  .  . 

2 

i675 

1677 

0.12 

B. 

Seed  mixed  with  smut;  treated  with 

360 

1128 

1488 

24. 

c 

•ic? 

in  ^6 

iSO^ 

IO. 

D. 

Seed  mixed  with  smut;  no  treatment. 

495 

565 

1050 

47- 

E. 

Seed  treated  with  hot  water  133°- 
135°  F.  for  15  min.;  smut  placed 
on  young  plants  before  appearing 
above  ground  

3 

106 

114 

7- 

F* 

Seed  treated  with  hot  water  133°- 
135°  F.  for  15  min.;  smut  placed 
on  young  plants  just  after  appear- 
ing above  ground  .... 

I 

345 

346 

o.^ 

G.* 

Seed  treated  with  hot  water  133°- 
135°  F.  for  15  min.;  smut  placed 
on  plants  when   about  two   feet 
high.    

o 

420 

420 

o. 

Hf 

Quite  smutty  seed  of  the  season  of 
1893  

509 

481 

990 

51. 

Examination  of  this  table  shows  that  hot  water  treatment  of 
ordinary  seed  has  again  given  the  uniform  result  of  the  preven- 

*  Seed  of  all  the  plants  was  planted  May  27.  Smut  in  water  was  squirted  on  the 
young  unrolled  parts  of  the  plants  in  plat  F.  on  June  13,  while  in  plat  G.  the  same  opera- 
tion was  performed  on  July  o,. 

t  A  different  variety  of  broom-corn  seed  than  that  used  in  any  other  experiment  in 
1895  or  1896,  but  from  the  same  lot  of  seed  as  was  used  in  1894. 


BROOM-CORN  SMUT.  399 

tion  of  smut.  The  same  seed  untreated  gave  an  unusually  large 
number  of  smutted  plants,  nineteen  per  cent.  With  the  seed 
mixed  with  smut  the  treated  part  showed  less  favorable  results 
than  in  any  of  the  previous  similar  experiments,  but  still  there  is 
a  very  decided  difference  between  it  and  the  untreated  part,  which 
had  over  fifty  per  cent.,  or  twice  as  much.  The  placing  of  smut 
on  very  young  plants  before  they  came  above  the  ground  gave 
rise  to  a  few  smutty  plants,  but  the  percentage  was  not  nearly  so 
great  as  it  would  have  been  had  the  smut  been  placed  on  seeds 
instead.  Placing  smut  on  the  young  parts  after  the  plants  had  ap- 
peared above  the  ground  gave  results  similar  to  a  previous  experi- 
ment— no  increase  in  smut. 

The  results  of  the  three  years  are  thus  seen  to  be  quite  uniform, 
always  showing  favorable  for  the  treatment.  The  only  seeming 
exception  is  in  the  case  of  treatment  of  very  badly  smutted 
seed.  Here  the  treatment  was  not  severe  enough  to  kill  all  of  the 
smut  spores,  and  the  varying  favorable  conditions  of  the  different 
years  or  ground  used  gave  rise  to  a  varying  amount  of  smut, 
though  never  to  nearly  so  great  a  per  cent,  as  in  the  same  seed 
untreated. 

Prevention  experiments  elsewhere.  In  the  literature  of  the 
smuts  of  the  sorghum  group  of  plants  the  only  prevention  experi- 
ments we  have  come  across  are  those  conducted  in  1891  by 
Kellerman  at  the  Experiment  Station  of  Kansas.  With  Ustilago 
Sorghi  of  sorghum  he  tried  seed  treatment  with  different  strengths 
of  solution  and  time  of  immersion  of  potassium  sulphid  and  chlo- 
rid  of  iron,  and  also  with  hot  water.  The  check  plats  gave  such 
a  small  per  cent,  of  smutted  plants  that  the  author  drew  no  con- 
clusions from  the  results  of  his  experiments.  In  the  two  cases 
where  he  used  hot  water,  however,  he  had  no  smutted  plants.  It 
is  stated  that  at  the  Khandesh  Experiment  Farm,1  of  India,  season 
of  1892,  copper  sulphate  treatment  of  seed  was  used  with  good 
results  in  preventing  a  common  smut  of  sorghum. 

EFFECT   OF   ENVIRONMENT   ON   PARASITE   AND   HOST. 

Some  interrogations.  What  are  the  environmental  conditions 
favorable  or  unfavorable  for  the  infection  of  a  plant  by  the  smut 
and  for  the  development  of  the  latter  afterward  ?  Such  conditions 
may  be  quite  general  or  quite  specific.  Some  years  or  certain 
localities  give  rise  to  badly  smutted  crops  and  we  say  the  general 
conditions  have  been  favorable  for  such  and  usually  ascribe  such 
conditions  to  the  presence  of  spores  with  the  seeds  and  to  the 

'Exp.  Stat.  Rec.  5:  354. 


400  BULLETIN  NO.  47.  [March, 

warm  moist  weather  at  the  infection  period.  But  there  are  other 
more  specific,  perhaps  largely  indeterminable,  conditions  than 
these  that  might  have  an  influence  in  determining  the  percent,  of 
smut  that  appears  in  the  plants.  Take,  for  instance,  very  smutty 
seed  ;  why  does  it  in  two  succeeding  years  in  the  same  locality 
show  the  variation  from  ten  (plat  4/95)  to  forty-seven  (plat  D,  '96) 
per  cent.?  Given  the  same  ordinary  seed  planted  but  a  few  days 
apart  on  plats  but  a  short  distance  from  each  other;  why  does  it 
show  the  variation  from  three  (plat  c,  '96)  to  nineteen  (plat  C,  '96} 
per  cent.?  In  1894  smutty  seed  a  year  old  was  planted  so  late  that 
the  plants  showed  but  a  few  immature  panicles  before  they  were 
killed  by  the  frost.  A  careful  examination  for  smut  in  the  one 
hundred  and  twenty-five  panicles  that  appeared  gave  three  with 
evidence  of  smut.  The  same  lot  of  seed  planted  at  the  proper 
time  in  1896  gave  over  fifty  (plat  H,  '96)  per  cent,  of  smutted  pani- 
cles. What  were  the  causes  of  this  difference  ?  Or  to  make  the 
case  extremely  specific  in  the  same  lot  of  seed  in  the  same  plat 
we  have  one  stalk  smutted  and  another  free.  Why? 

Environment  before  infection.  While  we  are  not  able  now  to 
cite  each  case  to  its  cause  or  causes,  yet  we  may  give  certain  con- 
ditions that  seem  to  have  a  greater  or  less  bearing.  Such  fall  into 
two  groups ;  namely,  those  that  are  favorable  or  unfavorable  to 
infection  of  the  host  by  the  fungus,  and  those  that  affect  the  rela- 
tionship of  the  two  after  infection.  Take  two  seeds,  for  instance, 
and  the  soil  immediately  surrounding  each.  One  or  more  of  the 
following  differences  in  condition  might  determine  why  one 
became  infected  and  the  other  not :  number  and  germinative  charac- 
ter of  the  spores  present;  amount  of  water  present;  character  of 
the  gases  in  the  soil  and  water  ;  chemical  character  of  the  soluble 
parts  of  the  soil ;  bacterial  development  as  unfavorable  for  pro- 
lific germination  of  spores  ;  nutrient  solutions  formed  from  manure 
and  decayed  vegetable  matter  as  a  source  for  prolific  formation  of 
sporidia ;  movement  of  water  as  a  means  of  bringing  germs  to 
infection-area  of  the  germinating  seed ;  heat  in  the  presence  and 
absence  of  moisture.  Or  the  conditions  of  the  seeds  themselves 
possibly  might  aid  in  deciding  the  matter;  namely,  age  of  seed 
as  affecting  character  and  vitality  of  germination  and  these  in  turn 
favorable  or  not  for  the  germs  present;  individual  character  or 
vitality  of  different  seeds;  heat  and  moisture  as  affecting  rapidity 
of  germination  and  character  of  tissue  formed  ;  depth  of  planting, 
etc.  as  affecting  length  and  character  of  epicotyl  and  leaf-sheath. 

Environment  after  infection.  Brefeld  has  shown  that  certain 
smuts  sometimes  succeed  in  entering  their  host  but  still  do  not 
succeed  in  forming  spores.  In  the  case  at  hand  the  fungus  sue- 


1897.}  BROOM-CORN   SMUT.  4OI 

ceeds  in  entering  the  germinating  plantlet  say  in  June,  while  the 
spore  masses  do  not  become  visible  in  the  flower  parts  of  the 
same  until  between  two  and  three  months  later.  May  there  not 
be  conditions  developed  during  this  time  that  are  favorable  to  the 
one  and  not  to  the  other?  May  not  outside  conditions  of  heat 
and  moisture  or  peculiar  hereditary  character  of  individual  plants 
favor  the  formation  of  plant  tissue  having  great  resistance  to  the 
penetrating  threads  of  the  fungus,  thus  conquering  it,  or  the 
reverse?  May  not  the  growing  point  of  the  plant  outstrip  in  up- 
ward growth  the  fungous  threads  and  thus  cut  them  off  from 
further  development?  Would  not  tardy  invasion  of  the  floral 
parts  prevent  or  lessen  the  spore  formation  ?  This  latter  question 
can  be  answered  in  the  affirmative,  if  we  count  the  evidence  pre- 
sented by  flowers  with  more  or  less  of  their  parts  infected  or  of 
panicles  with  only  part  of  the  flowers  infected,  apparently  the 
earlier  developed  being  free.  Such  conditions  and  results  are,  how- 
ever, with  our  present  knowledge  largely  matters  of  speculation. 

HISTORICAL   REVIEW. 

Bibliography.  The  following  list  includes  all  of  the  articles 
that  the  writer  has  been  able  to  find  in  which  mention  of  this 
smut  is  made.  The  references  are  reported  by  the  name  of  the 
fungus  used  rather  than  by  the  general  title  of  the  article,  except 
when  the  article  especially  treats  of  the  fungus. 

BARY,    A.   de.     Ustilago    Tulasnei.     Vergleich.    Morph.    u.  Biol.   der  Pilze   Mycet.   u. 
Bact.  369.     1884. 

Gives  Liebenberg  as  authority  for  germination   of  spores  after  being  in  her- 
barium six  and  a  half  years. 
BESSEY,  C.  E.     Ustilago  Sorghi  (Link)  Pass.     Neb.  Farmer  14:   189.    6  Mr.  1890. 

Notes  its  appearance  in   Nebraska,  and  recommends  blue-vitriol  treatment  of 
seed. 

BREFELD,  O.     Ustilago   Tulasnei  Kiihn   auf  Sorghum  -vulgar e.      Untersuch.  aus  dem 
Gesammt.  der  Mykol.  12:  120-122.  pi.  j.f.  iq-22.     1895. 

Gives  culture  experiments,  etc.  with  this  fungus. 
BURRII.L,T.  J.    Ustilago  Sorghi  (Link)  Winter.     Proc.  Am.  Soc.  Micr.  1888: — (12). 

Lists  this  smut  from  Illinois. 
COMES,  O.      Ustilago  Tulasnei  Kiihn.     Crittog.  Agr.  75.      1891. 

Gives  brief  note  as  to  hosts,  etc. 
DE-ToNI,  J.  B.     Ustilago  Sorghi  (Link)  Pass.     Syll.  Fung.  7s:  456.     28  O.  1888. 

Gives  description,  hosts,  synonyms,  etc. 
EVANS,  W.  H.     Sorghum  Smuts.     Handb.  Exp.  Stat.  Work.  326.     1893. 

Gives  a  brief  note  on  U.  sorghi. 

FAILYER,  G.  H.,  and  WILLARD,  J.  T.     Smut  in  Sorghum.     Exp.   Stat.   Kans.   St.   Agr. 
Coll.  16:   145.     1891. 

Mention  finding  two  kinds  of  Miiut  on  inmost  d  varieties  of  sorghum. 


402  BULLETIN  NO.  47.  March, 

FARLOW,  W.  G.,  and  SEYMOUR,  A.  B.     Ustilago  Sorghi  (Lk.)  Pass.     Prov.  Host-Index 
Fungi  U.  S.  154.     Je.  1891. 

Give  as  hosts  Sorghum  saccharatum  and  S.  vulgare. 

FISCHER  DE  WALDHEIM,  A.      Tilletia  Sorghi-vulgaris,T\\\.     Pringsh.  Jahrb.  7 :     106, 
in.     1869.— (Transl.  N.  Y.  St.  Agr.  Soc.  1870:  280.     1871.) 
Lists  this  fungus. 

FISCHER  DE  WALDHEIM,  A.      Ustilago    Tulasnei,  Kiihn.     Aper9u  System,  des  Ustil. 
12.     1877.— (Hedw.  16:  101.    Jl.  1877.) 

Gives  brief  description  with  synonyms. 
FRANK,  A.  B.     Ustilago  Tulasnei,  Kiihn.     Die  Krankh.  der  Pflanz.  431.     iSSo. 

Gives  brief  description,  distribution,  etc. 
FRIES,  E.     Sporisorium  Sorghi.     Syst.  Mycol.  3:  454-5.     1832. 

Gives  botanical  description  of  the  fungus  copied  from  Link. 

KELLERMAN,  W.  A.,  and  SWINGLE,  W.  T.     Notes  on  Sorghum  Smuts.     Proc.  Kans' 
Acad.  Sci.  12:  158.     1890. 

Note  distribution  of  Ustilago  Sorghi  in  U.  S.  and  give  hosts  in  Kansas. 
KELLERMAN,  W.  A.     Experiments  with    Sorghum   Smuts.     Exp.  Stat.  Kans.  St.  Agr. 
Coll.  23:  95-101. //.  2.     Ag.  1891. 

Gives  descriptions  of  U.  Sorghi  and  U.  Reiliana  and  results  of  infection  and 
prevention  experiments. 

KUHN,  J.      Die  Brandformen  der  Sorghum-Arten,  Tilletia    Sorghi,  Tul.  and   Ustilago 
cruenta,  Kiihn.     Hamb.  Gart.  u.  Blumenzeit.  28:  177—8.     1872. 

Briefly  discusses  the  two  forms,  of  which  U.  cruenta  is  described  as  new. 

KUHN,  J.     Ustilago  Tulasnei,  Kiihn.     Sitz.  nat.  Ges.  Halle  1874.— (Bot.  Zeit.  32:  122. 
20  F.  1874.) 

States  that  germination,  etc.  shows  the  fungus  to  be  an  Ustilago  rather  than 
a  Tilletia. 

KUHN,  J.     Die   Brandformen  der  Sorghumarten.     Mittheil.  d.     Vereins  f.  Erdkumlf. 
1877.— (Hedw.  17:  6-14.     Ja.  1878.) 

Gives  differences   between  the  smuts  so  far  found  on  Sorghum,  of  which   U. 
Tulasnei  is  named  as  one. 
LINK,  H.  F.     Sporisorium  Sorghi.     Linn.  Sp.  Plant.  6s:  86.     1825.     [ed.  Willd.] 

Describes  a  specimen  from  Egypt  on  Sorghum  rulgare,  being  the  first  printed 
account  of  our  fungus. 
LUERSSEN,  C.     Ustilago  Tulasnei,  Kiihn.    Handb.  der  System.  Bot.  1:  250.     1879. 

Gives  brief  specific  characters. 

NORTON,  J.  B.  S.     Ustilago  Sorghi  (Link)  Pass.     Trans.  Acad.  Sci.  St.  Louis  7:  231. 
pi.  25.f.  /-j.     9  N.  1896. 

Gives  note  on  germination. 
OUDEMANS,  C.  A.  J.  A.     Tilletia  Sorghi,  Tull.     Archiv.  Neerl.  8:  381.     1873. 

Notes  the  finding  of  this  at  Utrecht  in  1871. 

PRILLIEUX,  E.     Ustilago  Sorghi  (Lk.)  Pass.     Bull.  Soc.  Bot.  France  42:  36-39,  /.   a-e. 
Ja.  1895. 

Gives  structural  details  of  infected  body. 
RABENHORST,  L.     Tilletia  Sorghi,  Tul.     Hedw.  10:  18.     1871. 

Notes  the  collection  of  the  fungus  at  Kurdistan  in  the  orient. 

SCHROETER,  J.     Ustilago  Sorghi  (Link).      Krypt.  Flora  v.  Schlesien  31:  267.     1889. 
Gives  description  and  synonyms. 


7<?P7-1  BROOM-CORN   SMUT.  403 

SORAUEK,  P.      Tilletia  Sorghi  vulgar  is.     Handb.  Pflanzenkrankh.  259.     1874 

Makes  allusion  to  this  fungus. 
THUMEN,  F.  de.     Ustilago  Sorghi,  Pass.     Hedw.  12:  114.     Ag.  1873. 

Gives  description  of  this  as  a  new  species  with  Passerini  as  the  authority. 
TRELEASE,    W.     Ustilago    Sorghi   (Link).     Trans.   Wis.   Acad.    Sci.    Arts.    Letters    6: 
—1886. — (Prelim.  List  Par.  Fungi  Wis.  34.     N.  1884. 

Notes  distribution  of  the  fungus  in  America. 

TULASNE,    L.    R.      Tilletia   Sorghi-vulgaris.      Ann.   Sci.    Nat.  Bot.  III.  7:    116.  /.  j. 
f.  17-22.     1847. 

Describes  this  species  under  above  name. 

WEBBER,  H.  J.    Ustilago  Sorghi  (Link)  Pass.    Agr.  Exp.  Stat.  Neb.  I9:  69.    18  D.  1889. 
—  (Ann.  Rep.  Neb.  St.  Bd.  Agr.  1889:  214.     1890.) 

Notes  occurrence  of  this  fungus  in  Nebraska. 
WINTER,  G.     Ustilago  Sorghi  (Link).      Rabenh.  Krypt.  Flora  1:  90.     1884.     [and  ed.] 

Gives  specific  description,  synonyms,  etc. 

Exsiccati.  Specimens  of  the  fungus  have  been  distributed 
under  the  following  names  in  the  quoted  exsiccati. 

Ustilago  Sorghi,  Pass.     Thiimen  Herbarium  mycologicum  ceconomicum  63.     1873. 
Ustilago  Tulasnei,  K'uhn.     Rabenhorst  Fungi  Europaei  7997.     1875? 
Ustilago  Sorghi  (Lk.)  Wint.     Ellis  North  American  Fungi  1496.      1885. 
Ustilago  Sorghi  (Lk.).    Briosi  &  Cavara  Funghi  parassiti  delle  piante  coltivate  od 
utile  28.     1889. 

Ustilago  Sorghi  (Link)  Wint.     Roumeguere  Fungi  selecti  exsiccati 5128.     1890. 

Nomenclattire.  So  far  as  can  be  gathered  from  the  preced- 
ing references  the  history  of  the  fungus  is  as  follows:  In  1825 
Link  published  under  the  name  of  Sporisorittm  Sorghi  a  smut  on  a 
variety  of  sorghum  gathered  in  Egypt  and  communicated  by 
Ehrenberg.  The  fact  that  the  description  given  is  not  minute  and 
the  further  fact  that  several  smuts  have  since  been  found  on  the 
same  host  tend  to  make  it  uncertain  whether  this  description 
refers  to  what  is  now  commonly  called  Ustilago  Sorghi  or  not. 
This  uncertainty,  however,  is  dispelled  by  the  existence  of  the 
original  specimen  in  the  Berlin  Herbarium,  where  it  was  examined 
by  Ktihn  and  found  to  be  this  fungus.  The  next  reference  to  this 
species  that  could  be  found,  aside  from  the  copied  description  of 
Link  by  Fries  in  1832,  is  under  the  title  of  Tilletia  Sorghi-vulgaris 
by  Tulasne  in  1847.  This  specific  name  has  been  abbreviated  by 
some  authors  into  Tilletia  Sorghi.  In  1874,  however,  Kiihn 
showed  that  the  germination  of  this  fungus  put  it  in  the  genus 
Ustilago  rather  than  Tilletia,  and  he  renamed  it  Ustilago  Tulasnei. 
In  the  meantime,  in  1873,  another  supposedly  new  species  of  smut 
on  sorghum  was  described  under  the  name  of  Ustilago  Sorghi. 
Although  issued  by  de  Thiimen  in  his  exsiccati  and  described  by  him 
in  Hedwigia,  he  gave  Passerini,  the  collector,  as  authority  for  the 
name.  Fischer  de  Waldheim  in  1877  placed  this  name  as  a  syno- 
nym of  U.  Tulasnei,  thus  regarding  the  former  fungus  as  not 


404  BULLETIN  NO.  47.  [March, 

distinct.  Winter  (in  Die  Pilze)  seems  to  have  been  the  first  to 
have  placed  the  smut  in  the  genus  Ustilago  and  at  the  same  time 
to  have  used  the  earliest  specific  name  applied  and  the  authority, 
namely,  Ustilago  Sorghi  (Link),  for  the  same. 

However,  our  study  of  the  reproduction  of  the  fungus  shows 
it  to  be  a  Cintractia.  This  would  make  the  present  name  Cin- 
tractia  Sorghi  but  for  the  fact  that  De-Toni  has  already  referred 
the  Sorokine  fungus  (Endothlaspis  Sorghi)  questioningly  to  this 
genus  as  Cintractia  ?  Sorghi  (Sorok.),  thus  making  a  fungus  already 
of  that  name.  So  far  as  we  can  learn  the  identity  of  this  latter 
fungus  has  not  yet  been  further  worked  out,  either  as  to  its 
generic  position  or  its  relationship  to  the  smuts  already  reported 
on  the  sorghum-like  plants ;  yet  from  what  we  can  gather  from 
the  anatomical  description  and  figures  given  by  Sorokine  it  agrees 
in  general  with  our  fungus,  thus  increasing  the  belief  that  it  is  a 
Cintractia.  To  avoid  confusion  with  the  species  of  Sorokine, 
however,  we  present  the  second  specific  name  applied  to  the  fun- 
gus we  are  considering,  the  name  used  by  Tulasne,  which  gives 
the  following  arrangement,  Cintractia  Sorghi-vulgaris  (Tul.). 

SUMMARY. 

1.  Broom-corn  smut   is   a  parasite   belonging  to  the  lowest 
group  of  plants  called  fungi.     On  the  plants  very  closely  related 
to  broom-corn  this  and  several  other  smuts  have  been  found.     As 
is  shown  by  its  spore  formation,  this  smut  really  belongs  to  the 
genus  Cintractia  rather  than  to  Ustilago,  to  which  it  has  of  late 
years  been  referred,  and  Cintraciia  Sorghi-vulgaris  (Tul.)  is  the 
name  suggested  for  it. 

2.  Broom-corn  infected  \vith  this  fungus  produces,  as  a  usual 
thing,  brush  of  a  very  i.iferior  quality,  the  rays  being  scattered 
on  a  large  central  axis  instead  of  having  a  common  point  of  ori- 
gin.    Seed  formation  is  also  prevented  by  the  fungus   forming 
its  spores  in  the  young  ovaries  and  stamens.    Brush  gathered  with 
moisture  on  it  may  have  these  spores  settle  in  this  and  stick  to 
the   brush   when    it   dries,    thus   affecting   its   appearance.       The 
thrashing  of  infected  brush  is  disagreeable  because  of  the  dust 
formed  by  the  fungous  spores. 

3.  Broom-corn    only  becomes   successfully  infected   by  the 
fungus  while  the  seeds  germinate.     The  fungus  succeeds  at  that 
time  in   penetrating  the  very  young  tissues   usually  before  the 
plant  issues  above   the   ground,  and   the  fungous   threads  which 
have  thus   gained    entrance   increase   in  amount,  and  eventually 
closely  follow  the  upward  growth  of  the  stem  during  the  whole 


7^7-]  BROOM-CORN   SMUT.  405 

season.  When  this  is  about  completed  and  the  plant  begins  to 
develop  its  reproductive  parts,  the  fungous  threads  become  abun- 
dant just  beneath  the  epidermis  of  the  ovary  and  the  stamens.  This 
mass  soon  loses  its  identity  as  threads  by  the  gelatinization  of 
the  cell  walls  and  by  the  re-arrangement  of  cell  contents.  From 
this  fertile  stratum  the  spores  are  developed  centripetally.  Thus 
when  the  panicles  appear  we  find  their  stamens  and  ovaries  con- 
verted into  seed-like  bodies  filled  with  a  dusty  mass  of  spores. 
These  spores,  if  placed  immediately  in  water,  will  germinate  read- 
ily, a  condition  that  also  holds  true  for  those  that  are  a  number  of 
years  old. 

4.  Experiments  showed  that  the  amount  of  smut  ordinarily 
occurring  in  broom-corn  can  be  greatly  increased  by  mixing  a  lib- 
eral supply  of  smut  with  the  seed  before  planting,  but  was  not  in- 
creased by  planting  seed  in  land  that  had  smut  in  it  or  by  placing 
smut  on  the  plants  after  they  appeared  above  ground. 

5.  These  experiments  show  that  the  way  to  prevent  smut  is 
to  use  seed  free  from  it  or  seed  whose  attached  smut  germs  have 
been  killed.     This  killing  was  accomplished  by  treating  seed  with 
hot  water,    135°  F.,  for  ten  to  fifteen  minutes.      Ordinary  seed 
that  gave  with  check  experiments  from  two  to  nearly  twenty  per 
cent,  of  smutted  plants,  when  treated,  gave  plants  free  from  the 
smut.     Seed  mixed  with  abundance  of  smut,  when  treated,  pro- 
duced plants  while  not  always  free  from  smut  at  least  always  with 
a  much  smaller  per  cent,  of  infected  ones  than  similar  seed  not 
treated. 

PREVENTION   OF   BROOM-CORN   SMUT. 

For  the  convenience  of  those  who  may  wish  to  try  the  hot 
water  treatment  for  the  prevention  of  smut  in  their  broom-corn, 
the  following  method  of  procedure  is  suggested.  The  station  will 
be  pleased  to  receive  information  as  to  the  success  of  those  who 
may  try  this,  also  any  suggestions  for  improvement  that  use  may 
bring  out. 

Advisability.  From  the  experiments  conducted  it  is  seen 
that  smut  of  broom-corn  can  be  prevented  or  at  least  decidedly 
lessened  in  amount.  It  then  becomes  merely  a  question  with  each 
grower  to  decide  whether  or  not  the  injury  done  to  his  crop  dur- 
ing various  years  is  sufficiently  great  to  warrant  the  treatment. 
From  the  opinions  heard  expressed  on  this  matter,  it  would  seem 
that  most  broom-corn  raisers  think  that  methods  favorable  to  the 
prevention  of  smut  are  desired.  Beside  the  hot  water  treatment 
selection  of  seed  free  from  smut  is  a  means  to  the  same  end,  and 
one  that  is  generally  recognized,  although  the  reason  is  not  al- 


406  BULLETIN  NO.  47.  [March, 

ways  so  clearly  understood.  In  either  case  it  is  to  have  the  seeds 
free  from  living  germs  of  the  fungus  when  germination  takes 
place,  as  that  alone  is  the  time  when  the  smut  germ  can  success- 
fully infect  the  plant.  Selection  of  seed,  however,  unless  one 
knows  all  about  its  history,  is  not  safe,  as  by  mere  examination 
one  can  not  tell  whether  or  not  it  has  spores  present,  unless  it  is 
rendered  quite  smutty.  Hot  water  treatment,  on  the  other  hand, 
is  surer  and  involves  no  cost  save  the  labor  of  treatment.  As  the 
amount  of  broom-corn  required  to  seed  an  acre  is  comparatively 
small  the  treatment  is  not  nearly  so  tedious  as  is  the  quite  similar 
operation  with  oats. 

Hot  water  method.  The  following  is  recommended  as  a 
method  of  treatment,  mechanical  details  of  which  can  be  changed 
to  suit  the  convenience  of  the  operator.  A  reliable  thermometer 
and  two  vessels  of  hot  water  (one  at  a  temperature  of  about  135° 
F.,  and  the  other  at  135°  F.  with  means  for  keeping  it  there  either 
by  fire,  additional  hot  water  or  injection  of  steam)  are  needed  for 
the  operation.  The  seed  to  be  treated  to  the  amount  of  a  bushel 
or  less  is  placed  in  a  coarse  bag  which  is  immersed  in  the  first  ves- 
sel and  then  raised  up  and  down  until  the  seed  has  come  to  about 
the  temperature  of  the  water.  This  should  be  quickly  accom- 
plished and  is  done  so  that  the  temperature  of  the  second  vessel 
will  not  be  lowered  when  the  bag  is  placed  in  it.  This  is  now 
done,  and  the  temperature,  as  shown  by  the  thermometer  placed 
among  the  seeds,  should  be  kept  near  135°  F.  If  this  tempera- 
ture is  allowed  to  go  up  any  the  seed  is  in  danger  of  being  injured, 
and  if  it  goes  down  much  the  spores  may  not  all  be  killed.  After 
being  ten  to  fifteen  minutes  in  the  second  vessel,  the  seed  is  re- 
moved and  dried,  when  it  is  then  ready  for  planting.  While  it  is 
not  advisable  ever  to  use  very  smutty  seed,  if  such  is  used,  most 
of  the  smutted  kernels  may  be  removed  by  immersion  and  stir- 
ring in  water  and  then  skimming  off  the  floating  ones.  A  good 
many  perfect  seeds,  however,  are  apt  to  be  lost  by  this  operation, 
as  not  all  of  the  sound  ones  sink.  Hot  water  treatment  should 
then  be  given  the  seed. 

G.  P.  CLINTON,  M.  S. 

Assistant  Botanist. 

EXPLANATION   OF  ILLUSTRATIONS. 

Plate  I.  The  upper  engraving  shows  the  brush  from  a  plat  of  broom-corn  whose 
seed  was  mixed  with  smut  and  then  planted.  Over  ten  per  cent,  of  the  plants  were 
infected.  The  lower  engraving  shows  the  brush  from  a  plat  whose  seed  was  mixed  with 
smut  and  then  treated  with  hot  water  at  140°  for  15  minutes.  But  one  stalk  of  the  1321 
.stalks  in  this  plat  was  infected. 


BROOM-CORN   SMUT.  407 

Plate  II.  Upper  left  hand  engraving  shows  slightly  enlarged  smutted  flowers  of 
broom-corn.  Upper  right  hand  engraving  shows  panicles  of  broom-corn  ;  the  right  one 
was  free,  and  the  other  two  were  infected,  the  action  of  the  fungus  manifesting  itself  in 
the  enlarged  central  axes.  The  lower  engraving  shows  at  the  right  a  free  and  at  the  left 
an  infected  panicle. 

Plate  III.  This  shows  details  of  spore  infected  parts  of  broom-corn.  Figs,  i-io 
are  magnified  4  or  5  diameters,  figs.  11-13  about  10  diameters,  fig.  14  about  250  diameters, 
figs.  15-16  about  500  diameters. 

Figs.  1-9  show  infected  parts  of  flowers,  a.  stamens,  b.  pistil,  c.  scales.  In 
I  mycelium  was  found ;  in  2  spores  were  beginning  to  be  formed ;  in  3  stamens  were  free 
from  mycelium  and  spore  formation  had  just  begun  at  apex  of  pistil ;  in  4  stamens  and 
pistil  were  both  infected  but  free  from  each  other ;  in  5  the  infected  parts  were  blended 
together ;  in  6  stamens  and  pistil  merely  showed  distinct  at  apex  ;  7-8  show  rare  forms 
where  all  of  the  flower  parts  were  infected ;  9  shows  usual  method  of  infection  with 
glumes  free;  10  shows  an  drdinary  uninfected  seed  enclosed  in  the  glumes.  Figs.  11—13 
show  cross-sections  through  an  infected  body,  a.  false-membrane,  b.  mature  spores,  b1. 
immature  spores,  c.  columella.  Fig.  n  represents  section  through  apex,  12  through 
center,  and  13  through  base  of  the  infected  body  which  is  composed  of  pistil  and  sta- 
mens. Fig.  14  shows  cross-section  through  base  of  a  rather  young  infected  body,  a. 
representing  false  membrane  composed  of  epidermal  cells  and  sterile  fungous  threads,  b. 
mature  spores,  b.1  immature  spores,  c.  columella.  Figs.  15-16  show  more  highly  mag- 
nified sterile  fungous  cells  (a.)  and  spores  (b.),  fig.  15  being  drawn  from  smut  on  im- 
ported Chinese  variety  of  sorghum,  and  16  from  broom-corn. 

Plate  IV.  This  shows  the  mycelium  of  the  smut  in  the  tissues  of  broom-corn.  Fig. 
i  magnified  about  150  diameters,  and  Figs.  2-6  about  500  diameters. 

Fig.  i  shows  a  cross-section  through  the  epicotyl  of  germinating  broom-corn,  near 
union  of  epicotyl  and  leaf- sheath,  a.  representing  mycelium,  b.  epidermis,  c.  parenchy- 
matous  cells  of  cortex,  d.  woody  cells  of  central  cylinder.  Fig.  2.  A  more  highly  mag- 
nified part  of  i.  This  shows  condition  of  mycelium  about  three  weeks  after  spores  were 
placed  on  seed.  Fig.  3.  Section  through  leaf  near  juncture  of  leaf-sheath  and  epicotyl, 
showing  narrowing  of  mycelium  in  the  epidermal  cell  where  entrance  was  probably 
gained  to  the  leaf.  The  leaf-sheath  had  been  removed  and  spores  placed  on  base  of  the 
exposed  young  leaf.  Figs.  4-4'.  Mycelium  in  pith  cells  of  a  mature  plant,  4  from  base 
of  stalk  and  41  from  apex  near  panicle.  Fig.  5.  Mycelium  in  pith  cells  from  top  of 
stalk  at  time  flowers  are  being  formed.  Fig.  6.  Mycelium  in  pith  cells  46  days  after 
spores  were  placed  on  the  seed. 

Plate  V.  This  shows  germination  of  spores  of  broom-corn  smut,  a.  representing 
spores,  b.  pro-mycelium,  b1.  abstricted  portions  of  pro-mycelium,  c.  sporidia  and  second- 
ary sporidia,  c.1  germinating  sporidia.  Magnified  about  500  diameters. 

Fig.  I.  Germination  of  spores  in  distilled  water,  i  at  end  of  6  hours,  2  at  end  of 
9  hours,  and  3  at  end  of  24  hours.  Fig.  2.  Germination  of  spores  in  distilled  water  at 
end  of  24  hours,  showing  origin  of  knee-joints  and  infection  threads.  Fig.  3.  Germi- 
nation of  Kansas  spores  in  distilled  water.  Fig.  4.  Germination  in  distilled  water  of 
spores  taken  from  inside  of  seed  that  had  been  soaked  in  hot  water  at  130°  F.  for  5  min. 
These  spores  probably  germinated  in  contact  with  air.  Fig.  5.  Germination  at  end  of 
several  days  in  a  cell  with  only  a  film  of  water  covering  the  spores.  Figs.  6-8.  Germ- 
ination of  spores  in  different  fluids,  6  in  distilled  water,  7  in  tomato-broth,  8  in  beef- 
broth,  this  last  showing  only  the  condition  of  the  sporidia.  Figs.  9-11.  Germination 
of  spores  in  beef-broth.  9  at  end  of  19  hours,  10  at  end  of  22  hours,  and  n  at  end  of  40 
hours. 


408 


BULLETIN   NO.   47. 


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